A Cosmic History of Human Evolution

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(From the History and Astronomy/Cosmology pages.)


Early Evolution of the Known Universe

The evolution of the known Universe is most broadly divided by cosmologists into two eras. The first era began at the beginning of time with the creation of the known Universe in the Big Bang, about 13.799 billion years ago. It ended about 155 million years after the beginning of time with the ignition of the first stars. This first period is known as the "Primordial Era." Cosmologists call the subsequent period, the era beginning 155 million years ago in which we presently exist, the Stelliferous Era (literally, the "era of stars").

The First Seven Epochs of the Universe

The first seven "epochs" of time in the Primordial Era took place during the first three minutes and forty six seconds of the existence of the known Universe, and the first six of those epochs took place within the first second of time. The first period, called the "Planck Epoch," occurred when there was no space or time as we understand them. This is the epoch of the "proto-Universe" that "existed" just prior to the Big Bang. According to educated speculation based on an extrapolation of what would be expected under the Standard Model of Physics, at this "time" all four fundamental forces of nature (i.e., gravity, eletromagnetism, and the strong and weak nuclear forces) would have been unified in a perfect, static symmetry.

The Planck Epoch "ends," and time begins, with the separation of the Gravitational Force from the combination of the other three fundamental forces of nature. No one knows how or why this separation occurred but only that the gravitational force would have been, for theoretical reasons,[1] the first fundamental force to separate from the others, causing the Universe to come into existence as a "point-like" nucleation,[2] existing "everywhere" at once,[3][4] and containing all the energy of the Universe.

The Grand Unification Epoch followed the Planck Epoch at the beginning of time. During the Grand Unification Epoch, three of the four fundamental forces existed as the unified "Electronuclear Force." All the energy (and its equivalent mass) of the present day, knowable Universe (which consists of at least 100 billion galaxies, each containing an average of 100 billion stars and their associated planets),[5] was packed into four nominally massless[6] subatomic particles called Goldstone Bosons, each particle and its associated energy field representing one of the "four directions of freedom." These first four particles had a combined total volume billions of billions of times smaller than a present-day subatomic particle (itself a thousand billion times smaller than a grain of sand). The density of this point-like, early existence of the Universe is truly astonishing when one considers that our average-sized Sun, by itself, is large enough to contain approximately 1,300,000 Earth-sized objects, and that the energy and equivalent mass of billions upon billions of Sun-sized objects had to be packed into a volume billions upon billions of times smaller than a subatomic particle.[7]

Although, unlike the Planck Epoch, the Grand Unification Epoch was in fact an actual, measurable, period of time, the latter epoch ended after a period of time too small to imagine with the separation of the Strong Nuclear Force from the remaining Electroweak Force. Again, no one knows how or why the separation of the Strong Force occurred, only that the Standard Model of Physics requires that this would be the next force to separate.[8]

The separation of the Strong Nuclear force caused a faster-than-light[9] inflation of the Universe to occur, during what is aptly called the "Inflationary Epoch." "Spontaneous symmetry breaking" between the Strong Nuclear and the combined (and therefore still symmetrical) Electromagnetic and Weak Nuclear Forces resulted in the creation of the first particle of matter - the Higgs Boson - and the conversion of the four original, massless particles into slightly massive Nambu-Goldstone Bosons. The four Nambu-Goldstone Bosons subsequently interacted and combined with the field of the Higgs Boson as it decayed, creating the super-massive W+, W-, W0, and B0 Bosons of the unified Electroweak Force. All this was happening as "cosmic inflation" occurred, during which the space-time of the Universe expanded many times faster than the speed of light and became relatively flat and isotropic.

Even though the Inflationary Epoch lasted ten billion times longer than the previous Grand Unification Epoch, the Inflationary Epoch only existed for a mere one quadrillionth-of-a-quintillionth of a second but was relatively "long" compared to the much, much shorter time of the prior epoch. At the end of the Inflationary Epoch, the knowable Universe was everywhere, in its entirety, about the size of a grapefruit. Even though this is a very small size for something that had previously expanded at a speed many times the speed of light, this volume is proportionally so many times larger than what it had expanded from that expansion at this speed was adequately accommodated.[10] As such, this expansion must have occurred at a rate much faster than the speed of light to attain this relatively, much larger size in the incredibly short amount of time that the Universe existed during this period.

Although there only existed four W and B Bosons immediately after the "spontaneous symmetry breaking" of the Higgs Mechanism, the physics[11] of bosonic matter provide that these particles can exist within each other in the same way that light photons may superimpose upon and move through each other. Therefore, as the Universe rapidly expanded during inflation, the original four bosons quickly divided into countless W and B Bosons. The first quarks, known as Top Quarks, came into existence as some of the W and B Bosons decayed. As such, the Top Quarks became the first extremely massive fermions - i.e., the first truly massive particles of matter. As the Universe rapidly cooled during inflation, Electroweak Symmetry was broken and the W0 and B0 Bosons of the Electroweak Force finally coalesced to form the W+/- and Z0 Bosons of the Weak Nuclear Force and the Photons of Electromagnetism.

The Electroweak Epoch began approximately one quadrillionth-of-a-quintillionth of a second after the beginning of time and lasted for approximately one trillionth of a second. During this time, the expansion of the Universe abruptly slowed and the W and Z bosons, as well as the Top Quarks, finally decayed into the less massive quarks, which would later come to compose the protons and neutrons of ordinary matter. Also emerging from the decaying W and Z Bosons and Top Quarks were the leptons (electrons, neutrinos, and their associates), albeit in the form of an extremely high energy, electrified, quark-gluon plasma that filled the entire Universe, which was still unimaginably dense and massive. Although the Universe has continued to expand at an ever-increasing rate to the present day and will for all time to come, a rapid slowing of the speed of expansion of the Universe that occurred during the Electroweak Epoch caused the Universe to experience a period of "cosmic reheating." The Electroweak Epoch ended with the final separation of the Nuclear Weak Force from the Electromagnetic Force, creating a plasma in which there existed a hyper-dense and very intimate mixture of photons, neutrinos, electrons, quarks, gluons, pi mesons, and other more exotic leptons and bosons, everywhere throughout the potentially infinite, grapefruit-sized Universe.

The Quark Epoch began one trillionth of a second after the beginning of time, when the entire mass of the Universe had come to exist as a nearly "uniform," and extremely dense, electric, quark-gluon plasma, described by some physicists as a "sizzling sea of quarks." The gluons, photons, and pi-mesons were without mass and, in the case of the neutrinos (which have a very small mass), without "sufficient force to separate the individual quarks from each other so that they blended seamlessly together into one seething mass of particles. This epoch ended approximately one one-hundred-thousandth of a second later when the temperature of the Universe dropped below the binding energy of quarks, causing all the quarks in the Universe to form relatively independent Hadrons, albeit still connected with each other via the electric plasma that permeated the entire Universe at that time. The Hadrons created were primarily the protons and neutrons, also known as Baryons, which are Hadrons composed of three quarks each.[12] These Hadrons are the subatomic particles that comprise ordinary matter. Also present at this time were the very energetic Hyperons, which are Hadrons containing an exotic, high-energy particle called the "Strange Quark," but those very quickly decayed. The formation of all these Hadrons is a process called "Baryogenesis."

The Hadron Epoch began at approximaely one one-hundred-thousandth of a second after the beginning of time. At the beginning of this period, protons, neutrons, and electrons were interacting in the form of a dense, almost universally uniform, nuclear, electrified plasma. In this epoch, the positive matter hadrons eliminated their antimatter hadron counterparts, creating the presently unexplained asymmetry of the absence of antimatter hadrons in the observable Universe. This epoch ended approximately one second later when the almost masslesss and very weakly interacting neutrinos decoupled from the plasma and began traveling, relatively independently, through it. This caused the Universe to become "transparent" to neutrinos, although the Universe was still "opaque" to electromagnetism - i.e., opaque to light as in a very bright, dense fog.

The Lepton Epoch began approximately one second after the beginning of time and lasted about three minutes and 45 seconds. During the first three minutes of this epoch, the remaining antimatter leptons (i.e., the electrons and neutrinos) were eliminated by positive matter, cancelling each other out to become very energetic bursts of light in the form of gamma rays. This cancelling out of the antimatter leptons created the presently unexplained asymmetry of the absence of antimatter leptons in the observable Universe.

The Photon Epoch and the Dark Ages of the Universe

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At the end of the Lepton Epoch, all the matter in the Universe existed as a giant, electrified, dense cloud of protons, neutrons, and electrons, which glowed brightly like a universal, cosmic neon sign. Three minutes after the beginning of time, neutrons and protons were able to combine as a radioactive isotope of Hydrogen called Deuterium.

Over the next 30 minutes and 55 seconds after the Lepton Epoch, ordinary Helium nuclei formed from the Deuterium nuclei, so that Helium came to constitute about 26% of the cosmic gas cloud in a process called "nucleosynthesis." The rest of the gas cloud at this time consisted of ordinary Hydrogen, with trace amounts of the radioactive isotopes of hydrogen - Deuterium and Tritium.[13] Besides the ordinary, visible matter existing at this time, the remaining mass of the Universe existed, and still exists, predominantly in a still-unknown (and directly unobservable) form as "Dark Matter" (see below).

Approximately 34 minutes and 40 seconds after the Big Bang, the primordial Universe had formed, consisting of about 74% Hydrogen, 26% Helium-4, and 0.1% Deuterium and Helium-3 nuclei, with trace amounts of Tritium and the next two elements in the Periodic Table, Lithium and Beryllium. At this time, all the matter of the Universe existed as a nearly uniformly dense cloud of ionized gas composed of only these elements. This first thirty minutes of the Universe succeeding the Lepton Epoch is the beginning of the period of time cosmologists call the "Photon Epoch."

During the Photon Epoch, the Universe remained extremely bright and hot due to the interaction of photons with the surrounding matter. The newly created elements existed together in a relatively dense, gasseous, electrical plasma. This means that, during this period, enormous electrical discharges similar to lightning permeated the entire Universe. In this state, all the Hydrogen and Helium atoms that existed in the Universe were entirely ionized - i.e., no electrons were bound to the atomic nuclei - and the primordial atoms were electrically charged (a +1 electric charge for Hydrogen and +2 for Helium).

At approximately 70,000 years after the beginning of time, the densities of non-relativistic matter (i.e., relatively slow-moving atomic nuclei) and relativistic radiation (i.e., very fast-moving photons, neutrinos, and high energy electrons) were about equal. The Jeans Length is a measure of the tension that existed between the inward gravitational attraction of the mass of the gas cloud for itself as balanced against the outward pressure effects caused by the streaming radiation of the heat.

As the Universe expanded and the cosmic gas cloud cooled, the Jeans Length grew shorter because the inward pressure due to gravitation was no longer overcome by the outward pressure due to the heat of the gas. As the Jeans Length grew shorter, perturbations in the uniform gas cloud, instead of being wiped out by free-streaming radiation, began to grow in amplitude. Consequently, this "Jeans Instability" was the cause of tiny inhomogeneities (i.e., inconsistencies) in the formerly uniform, Universal cloud of hydrogen and helium gasses.

According to ΛCDM (the Lambda-Cold Dark Matter Model), at this stage cold Dark Matter came to dominate the Universe, paving the way for gravitational collapse to amplify the tiny inhomogeneities left by cosmic inflation. This gravitational collapse made dense regions of the cosmic gas cloud denser and rarefied regions more rarefied, resulting in an overall, universal, web-like composition to the largest structures of what would later become the galactic super-clusters of stars. However, because present theories as to the nature of Dark Matter are inconclusive, there is as yet no consensus as to Dark Matter's origin at earlier times or its present constitution, as currently exists for ordinary matter.

The entire cosmic gas cloud did not condense entirely in on itself because the Universe continued to expand at an ever increasing rate which continues to this day. The cause of the continual increase in the cosmic rate of expansion is not known and has therefore been called "Dark Energy."

Beginning at about 83,000 years after the beginning of time, the photons of the Universe became able to travel freely without constantly interacting with the other atomic nuclei and subatomic particles. This caused the Universe to begin the process of becoming transparent, albeit still brightly lit by discharges of electrical energy in what appeared then as a milky white, cosmic gas cloud.

As the Universe cooled, somewhere between approximately 240,000 to 310,000 years after the Big Bang, the previously free-streaming electrons of the electrical plasma began to be captured by the positive atomic ions, making the resulting atoms electrically neutral (a process that occurred more quickly for helium than for hydrogen), in a process known as "recombination." At about 378,000 years after the Big Bang, recombination was finished and the overall Universe became electrically neutral, ending the period of time when the Universe was dominated by the electrical discharges of a cosmic plasma. The Universe was now completely transparent and dark, ushering in the so-called "Dark Ages" of the Universe.

The photons emitted immediately after recombination that could travel relatively undisturbed throughout the Universe are those that we presently observe as the Cosmic Microwave Background (CMB) present throughout the Universe. The CMB is only viewable with special instrumentation because microwaves are not visible to the naked eye. The CMB, itself, is a presently observable picture of the Universe as it existed after recombination at approximately 378,000 years after the Big Bang, slightly more than 13.799 billion years ago.

Since then, the average temperature of the present-day Universe has cooled to approximately 2.735 Kelvin and continues to cool, albeit very, very slowly. Clumpings in the cosmic gas cloud due to gravitational collapse and the continued enlargement of perturbations proceeded to condense those clumpings to the point where gravitational forces caused the hydrogen nuclei in many of the gas clouds to fuse. This fusion first occurred about 155 million years after the Big Bang, forming helium and igniting the first very giant stars, which burned fast and hot and, after only tens of millions of years, exploded as supernovae, leaving super-massive black holes in their wakes. These super-massive black holes then became the centers of newly forming galaxies of stars.

Ignition of the first stars lit up the Universe and ended the so-called Dark Ages. Smaller gas clouds also condensed, resulting in the much longer-lasting, first generation of main sequence stars, similar to our own Sun. If we compress the entire timeline of cosmic history from the Big Bang until the present into a time period of one 365-day year of a Cosmic Calendar (where the present time would be the last second of the last day of the last month of the Cosmic Year) then the first stars ignited sometime very early on January 5th of the Cosmic Calendar.

With the ignition of the first stars, the Photon Epoch was now over, completing that part of the cosmic timeline known as the "Primordial Era." The first quasars which emerged from the super-massive black hole at the center of the newly forming galaxies significantly re-ionized and re-heated the Universe, which then again, briefly, existed in a plasma state, before starting to cool once more (a "second re-heating" of the Universe).

The first small galaxies formed about 200 million years after the Big Bang (sometime in the early hours of January 6th of the Cosmic Calendar). Our own galaxy, the Milky Way, formed from successive collisions of other smaller galaxies almost two and one-half billion years after that (sometime around midnight on March 8). After several billion years, the first generation of main sequence stars had exhausted their hydrogen fuel supply. If near white dwarf stars, the dying stars were re-ignited by the white dwarfs as Novae or, if massive enough, as Type Ia Supernovae. Otherwise, these first stars died more slowly as expanding Red Giants. If the stars had masses that exceeded ten solar masses in size[14] (as most of the early stars did) then their lifespans were much shorter, on the order of tens-of-millions of years, and they exploded as most of the other types of Supernovae do and spread the products of their nuclear fusion into the surrounding Universe.

The first generation of main sequence stars that ended as Type Ia supernovae produced the elements Helium through Iron on the Periodic Table of the Elements as the products of the nuclear fusion of Hydrogen atoms in their cores, which were spread back out into the surrounding area after the supernova explosion, creating new star-forming nebulae.[15] The first generation of very massive stars that exploded as supernovae due to core collapse after only tens-of-millions of years were an abundant source of elements up through Uranium. Gravitational forces continued to pull the galaxies together into groups, clusters, and super-clusters, which then orbited each other, creating the largest structures in the Universe.

Materials ejected from the first supernovae condensed to form the first rocky planets and a second generation of stars. Because of the abundance of the heavier elements in our Earth and Solar System, scientists believe that our Sun is at least a third-generation main sequence star. This explanation (and the age of our own Sun) is consistent with the observed age of the Universe at approximately 13.799 billion years. Due to the absorption of matter ejected from previous supernovae, the Earth is composed of the elements up through Uranium on the Periodic Table.

Development of the Solar System

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Our solar system began to form about 9.1 billion years after the beginning of the Universe, and the Earth itself is about 4.54 billion years old. The Solar System formed from the gravitational collapse of a giant molecular cloud, known as the Pre-Solar Nebula. The Pre-Solar Nebular, itself, was formed from the remnants of the death of a previous star that had ended its existence in a supernova explosion. The initial gas cloud was likely several light-years across in size, contained several smaller nebulae, and probably birthed other stars beside our own, forming a kind of stellar nursery.

As our portion of the Pre-Solar Nebula began to collapse, the conservation of angular momentum made it rotate faster. The center of the collapsing portion of the nebula, where most of the mass collected, became increasingly hotter than the surrounding disc. Regions of the gas cloud containing elements heavier than helium moved into the regions of the gas cloud outside the hotter central region and eventually formed the rocky planets and cores of the gas giants due to the greater masses of those elements. As the contracting nebula rotated, it began to flatten into a spinning proto-planetary disc with a diameter of roughly 200 astronomical units (abbreviated "AU").[16] Consequently, a hot, dense, protostar formed at the centre of the nebula. This was the birth of our Solar System, approximately 4.7 billion years ago (about 9:20 p.m. on August 28 of the Cosmic Calendar).

At this point in the beginning of its evolution, the Sun is believed to have been a T-Tauri-type star. Studies of T-Tauri stars show that they are often accompanied by discs of pre-planetary matter with masses of 0.001 to 0.1 solar masses, with the vast majority of the mass of the nebula located in the star itself. The planets of our solar system formed by the accretion of matter from the proto-planetary disc of a T-Tauri-type star which later became our Sun.

Within 50 million years of the formation of the proto-planetary disc, the pressure and density of hydrogen in the center of the proto-star became great enough for it to begin thermonuclear fusion of its hydrogen gas, forming helium at its core about 4.57 billion years ago (at about 7:45 a.m. on September 1 of the Cosmic Calendar). The temperature, reaction rate, pressure, and density of the Sun increased until hydrostatic equilibrium was achieved, with the thermal energy produced by the nuclear fusion countering the force of gravitational contraction. At that point, the Sun became a full-fledged, main sequence star. Therefore, the Sun is a continuous thermonuclear explosion that will remain stable for almost 10 billion years and which is presently about 4.5 billion years old.

The Earth and the other planets of the Solar System formed approximately 4.54 billion years ago (about 19 hours after ignition of the Sun on the Cosmic Calendar, or approximately 2:45 a.m. on September 2) from the accretion of solid matter and gasses orbiting the solar system in the Sun's proto-planetary disc, now called the Solar Nebula, consisting of the gasses and dust left over from the Sun's formation. The currently accepted method by which the planets formed is known as accretion, in which the planets began as dust grains in orbit around the central protostar. Through direct contact, these grains formed into clumps up to 200 metres in diameter (asteroids), which in turn collided to form larger bodies (planetesimals) of up to approximately 10 kilometres (km) in diameter. These planetesimals gradually increased in size through further collisions with other matter in the solar nebula, growing in diameter at the rate of several centimetres per year, or growing more dramatically when the larger bodies directly collided, over the course of the next few million years.

The Inner Solar System - the region of the Solar System inside 4 AU - was too warm during the time of the formation of the planets for large amounts of volatile molecules like water and methane to condense into liquid form within that region of the Solar System so as to create the large gas giants typical of the outer solar system. Therefore, the planetesimals that formed there at that time could only form from compounds with high melting points, such as metals (like iron, nickel, and aluminium) and rocky silicates. Subsequent collisions and mergers between these planet-sized bodies allowed the terrestrial planets to grow to their present sizes, and these rocky bodies became the planets Mercury, Venus, Earth, and Mars. The elements heavier than helium are quite rare in the universe, comprising only 0.6% of the mass of the Solar Nebula, so the terrestrial planets could not grow very large. By about 100,000 years after the ignition of the Sun, the terrestrial embryos of the four inner planets had grown to about 0.05 Earth masses each. The planets further than 4 AU, past the astroid belt that encircles the inner, terrestrial planets, retained all their gasses and became the "gas giants" of the outer solar system.

When the terrestrial planets were forming, they remained immersed in a disk of gas and dust. The gas was partially supported by pressure and so did not orbit the Sun as rapidly as the planets. The resulting drag caused a transfer of angular momentum and, as a result, the planets gradually migrated to new orbits. Models show that temperature variations in the disk governed this rate of migration, but the net trend was for the inner planets to migrate inward as the disk dissipated, leaving the planets in their current positions after all the matter in their orbits had been accreted by those planets.

Scientists have been able to reconstruct relatively detailed information about Earth's past. The earliest dated Solar System material was formed 4.5672 ± 0.0006 billion years ago and, by 4.54 billion years ago (within an uncertainty of 1%), the Earth and the other planets in the Solar System had formed out of the Solar Nebula. The Moon formed shortly thereafter, approximately 4.53 billion years ago (about six and 1/2 hours after the formation of the Earth on the Cosmic Calendar). Thus, the assembly of the Earth through accretion was largely completed within a period of 27 million years. This means that the entire period of time on the Cosmic Calendar from the formation of the Pre-Solar Nebula to the Formation of the Earth lasted a little more than four days, from about Noon on August 29 until about 8:30 a.m. on September 3. Initially molten, the outer layer of the planet Earth cooled to form a solid crust and water vapor in the atmosphere began condensing to form the first oceans.

The current consensus model for the formation of the Moon is the Giant Impact Hypothesis. According to this hypothesis, about fifty million years after the creation of the solar system, the Moon was created when a Mars-sized object (sometimes called Theia) impacted the Earth with a glancing blow. In this model, a very large portion of this object's mass would have merged with the Earth, giving the Earth a mass that is nearly its present size, and a portion would have been ejected into space, with enough material sent into orbit to coalesce into the Moon.

Outgassing and volcanic activity produced the primordial atmosphere of Earth. Condensing water vapor, augmented by ice and liquid water, delivered by asteroids and the larger proto-planets, comets, and trans-Neptunian objects, produced the oceans. The newly-formed Sun was only 70% of its present luminosity, yet evidence shows that the early oceans remained liquid, instead of freezing — a seeming contradiction that has been dubbed the Faint Young Sun Paradox. However, a combination of greenhouse gases and higher levels of solar activity probably served to raise the Earth's surface temperature, preventing the oceans from freezing over. By 3.5 billion years ago, the Earth's magnetic field was established, which helped prevent the atmosphere from being stripped away by the "solar wind" and directed the otherwise harmful, ionized particles, ejected by the Sun, away from the Earth's surface.

Two major models have been proposed for the rate of continental growth on the Earth's surface: steady growth to the present-day and rapid growth early in Earth's history. Current research shows that the second option is most likely, with rapid initial growth of continental crust followed by a long-term, relatively stable, continental surface area. On time scales lasting hundreds of millions of years, the terrestrial surface continually reshaped itself as various continents formed and broke up due to the action of plate techtonics. Consequently, the primordial continents migrated across the surface of the Earth, occasionally combining to form what have been called supercontinents, and then breaking up again into smaller, constituent continents.

Evolution of Life on Earth

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Geologic time on Earth (the time from the Earth's formation until the present day) is most broadly divided by geologists into two periods. First there is Precambrian Time, which is composed of three eons: the Hadean Eon, prior to the formation of the Earth's crust; the Archaen Eon, during which the first, unicellular, living organisms evolved; and the Proterozoic Eon, during which the first sexually reproducing, multicellular life forms evolved. The second broad period is the Phanerozoic Eon (the fourth eon of geologic time), during which modern, multicellular life forms evolved. The Phanerozoic itself is divided into three eras: the Paleozoic, Mesozoic, and Cenozoic, the last of which includes our present time.

Precambrian Time

During the Archaen Eon, when the Earth's crust was first fully formed (about 4 billion years ago, which is sometime early on September 16 of the Cosmic Calendar), the Earth had a "reducing" atmosphere, very different from Earth's present "oxidizing" atmosphere. Unlike the present-day Earth atmosphere composed predominantly of nitrogen and oxygen, the early Earth had an atmosphere consisting predominantly of ammonia, methane, carbon monoxide, hydrogen sulfide, sulfur dioxide, and water vapor, which were common gasses in the solar nebula.

Because the Earth contains a molten iron mantle and nickel core, a magnetic field exists over the Earth that shields the atmosphere from being stripped by the "solar wind" of magnetically charged particles emanating from the Sun. In addition, the presence of the moon stabilizes Earth's rotation, which ensures a persistent heating and cooling cycle due to regular periods of approximately twelve hours of light and twelve hours of dark at the Equator. The Earth also has a tilted axis that ensures the cycle of different seasons in the more northern and southern latitudes during the Earth's orbit about the Sun.

The Earth's surface was still very hot, and the turbulent movement of the atmospheric gasses surrounding the Earth (due to the Earth's rotation and the convection of rising hot and falling cool gasses) caused friction in those gasses and spawned the first lightning storms on Earth. The energetic discharge of lightning in the primordial clouds, as well as the heat of geothermal processes, caused the formation of the first amino acids, nucleic acids, simple sugars, and hydrocarbons from the atmospheric gasses, and these substances then rained down into the primordial oceans.

Over millions of years this process continued until the newly formed oceans were full of those complex molecules. The reaction of the individual molecules of these substances with heat and lightning caused many of them to link together, forming the first, very simple, polypetide and RNA chains. After tens-of-millions of years, the polypeptide and RNA chains spontaneously developed enzymatic properties. Some of the early enzymes were powered by naturally occuring, energy storing, phosphate molecules (similar, if not identical to, present-day ADP and ATP) freely present in the environment and that had formed spontaneously under the energetic conditions of the early reducing atmosphere.

Eventually, other enzymes developed properties that allowed them to metabolize the simple carbohydrates and hydrocarbons that were also natural products of the primordial energy present in the primeval Earth. These natural carbohydrates were abundantly present in the primordial ocean and were used by the first enzymes for the production of more ATP, or its ancestral, chemical predecessor. The energy for the production of ATP or ATP-like molecules in these early enzymatic systems would have been solely derived from the atmospheric and geothermal energy that was abundant in the early Earth.

Eventually, some of these enzymatic properties acted to cause some of the polypeptide or nucleic acid chains to propagate themselves, possibly in a manner similar to the modern day viroid or prion. After a longer time, some of the self-propagating RNA chains specialized as templates for propagating other RNA chains, possibly with the assistance of some of these early enzymes. After an even longer time, the templates became more sophisticated and certain proteins specialized in transcribing the nucleic acid chains into other protein enzymes that were themselves coded into the RNA templates. This was the birth of the probable first organelle, the ribosome. No cells were yet created and the oceans were one very large protoplasm filled with these very dynamic chemicals, all interacting with each other.

When certain, cooperating, conglomerations of enzymes and nucleic acid chains propagated better by becoming encapsulated in lipid micelles, selective pressures favored the production of micelles that could be engineered by enzymes that functioned to maintain those membranes, and the first very primitive cells were born. After the formation of the first cells, the process of maintaining the RNA strands became more sophisticated. Eventually, the more stable DNA molecule replaced RNA as the coding template in all non-viral organisms. RNA also continues to operate as the sole mechanism for the transcription and translation of DNA, in the form of messenger and transfer RNA. In addition, the enzymatic properties of RNA continue to be used by transfer RNA and the ribosome enzyme.

Mutations in the DNA template, along with the actions of newly created enzymes in the environment, facilitated the development of enzymes that formed and maintained ever more sophisticated cell membranes and the creation of cytoskeletons and cell walls. Cell enzymes that were responsible for the replication and propagation of DNA templates became more cooperative with the enzymes that created and maintained cell membranes and the process of cell division came into being. The Last Universal Common Ancestor (LUCA) evolved sometime before the appearance of the oldest stromatolite fossils, by about 3.5 billion years at the latest (sometime on or about 2:00 p.m. on September 29 of the Cosmic Calendar), due to the evolutionary imperative that DNA should become the predominant form of genetic inheritance.

As the Earth cooled, sugars and hydrocarbons produced abiotically by the energy of the primordial Earth became less abundant. Competition for the increasingly scarce sugars and hydrocarbons selected for cells that could capture light energy from the Sun to phosphorylate freely available AMP molecules to form ADP and ATP. Other cells had evolved that could produce carbohydrates and lipids from the energy stored in environmental ATP or the ATP produced by some cells and then canibalized by other cells.

Eventually, primitive photosynthetic cells adopted the enzymatic processes of carbohydrate and lipid production and became an anabolic food source for catabolic cells that fed upon them. Development of the first, photosynthetic, cyanobacteria occurred within a billion years of the birth of LUCA, about 2.5 billion years ago (on October 26 of the Cosmic Calendar). Oxygen production by the first photosynthetic organisms precipitated the first major extinction event[17] - the "Oxygen Catastrophe" - when an abundance of atmospheric oxygen caused the extinction of most of the bacteria that had formerly depended on an anaerobic atmosphere for their existence. Because there was no "sink" for the absorption of the newly accumulated oxygen, the Oxygen Catastrophe proceeded rapidly (within approximately 50 million years) and occurred about 2.3 billion years ago (October 30).

The predominance of Oxygen and the absence of the greenhouse gas Carbon Dioxide led to the first and greatest glaciation in the Earth's existence, the so-called "Snowball Earth" event. The development of photosynthesis and the resultant oxygenated atmosphere also permitted the development of a much more powerful aerobic catabolism that, unlike anaerobic catabolism, could use the atmospheric oxygen to squeeze many times more energy out of energy rich macromolecules through a complete oxidation of those molecules to carbon dioxide, something that was not chemically possible in the anaerobic process. The increase in Carbon Dioxide production due to the development of aerobic metabolism increased the amount of Carbon Dioxide in the atmosphere (a by-product that was very poorly produced by the pre-existing anaerobic metabolism), which led to a warming of the planet and an end to the Snowball Earth event.

Certain catabolic cells became specialists at metabolizing carbohydrates. When those cells became symbiotic with other cells and eventually came to permanently reside in those other cells, the first mitochondria came into existence. When the specialists at using light energy for metabolic purposes were ingested by and became symbiotic with other cells, the first plastids were born. Eventually, the same thing happened with cells that became experts at storing, transcribing, and replicating DNA chromosomes. When the DNA expert cells were captured and used by other cells as a way of storing and protecting their own DNA strands, the first cell nuclei and eukaryotic cells evolved, ushering in the Proterozoic Eon. The first eukaryotic cells appeared probably about 2.2 billion years ago (about 10:00 p.m. on November 2 of the Cosmic Calendar),[18] as well as the first multicellular arrangements of eukaryotic cells shortly thereafter. The first "modern" eukaryotic protists and simple algae evolved about 1.8 billion years ago (about 11:45 a.m. November 13 of the Cosmic Calendar).

Some of the eukaryote protists developed flagellae, which assisted with the procurement of food in the environment. Some protists then developed the use of internal microfilaments to effectuate the use of pseudopodia for movement or the use of a single flagellum for movement. Movement greatly enhanced the ability to procure food through predation and with the exchange of genetic material in a manner similar to plasmid exchange between prokaryotes, thereby significantly enhancing the process of evolution.

About 1.5 billion years ago (about 9:50 a.m. on November 21 of the Cosmic Calendar), some of the early, catabolic, eukaryotic protists had developed chitinous cell walls that became the first aquatic fungi. Later, loosely cooperative, multicellular arrangements of eukaryotes occurred and presaged the split between fungi and the common ancestor of all animals. Sexual differentiation and meiotic cell division appeared soon after, about 1.2 billion years ago (about 8:00 a.m. on November 29).

In the case of the evolutionary ancestor of animals, the more highly specialized use of internal, cellular microfilaments permitted a sophisticated intracellular organization that permitted increasingly complex arrangements of multicellular tissues and the first animals. The earliest animals aggregated actin bundles into a filter-feeding collar around a cilium or flagellum that further facilitated the acquisition of environmental nutrients. About 850 million years ago, complex multicellular arrangements of photosynthetic cells and the use of cellulose for cell walls formed the common ancestor of all plants in a marine environment.[19]

About 700 million years ago (about 1:00 p.m. on December 12 of the Cosmic Calendar), aquatic, multicellular arrangements of catabolic, eukaryotic cells, descending from a common ancestor with the fungi but lacking chitinous cell walls, evolved into the first marine animals (probably similar to modern-day colonial Volvox). These very primitive multicellular organisms eventually developed into ancestral sponges. Some of the later, truly motile animals developed true, differentiated tissues and The a rudimentary nerve net led to the evolution of jellyfish and comb jellies. After this came the development of an embryo that passed through a gastrula stage of development to form the first marine eumetazoans ("true animals") with true digestive organs (a "gut").

The first terrestrial fungi (the first living organisms to live on dry land after the bacteria) appeared about 635 million years ago (on or about December 15 of the Cosmic Calendar). Soon after followed the development of lichens. The "higher" terrestrial fungi, with differentiated tissues and organ structures, first appeared about 570 million years ago, ushering in the fourth eon of geologic time - the Phanerozoic Eon - on or about December 16.

The Phanerozoic Eon

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Sometime between about 580 to 530 million years ago, a multitude of invertebrate forms of marine life greatly diversified, during an event that has been called the "Cambrian Explosion." This represents a period of evolution where the development of dentition among some of the soft-bodied, worm-like animals which lived at that time caused adaptive pressures on the prey of those newly-toothed animals so that the prey developed hard shells (exoskeletons) to better ensure their survival, the most famous of which are the now-extinct trilobites. Because the hard-shelled animals left direct, fossile evidence of their existence,[20] there appears to be an "explosion" of the appearance of new life forms in the archeaological record.

The "event" of the Cambrian Explosion marks the beginning of the Cambrian Period of the first era of the Phanerozoic Eon, known as the Paleozoic Era. This period also included the evolution of the primordial ancestors of modern-day filter-feeders, such as corals, brachiopods, and molluscs, with the deuterostomes splitting from the protostomes about 558 million years ago. Marine arthropods, with true nervous, circulatory, and respiratory systems, as well as sophisticated sensory organs and exoskeletons, first appeared about 542 million years ago (by December 17 of the Cosmic Calendar). The first chordates evolved from the early deuterostomes about the same time as the marine arthropods. True central nervous systems were soon followed by the development of crania to protect the primitive brains of chordate nervous systems.

The next period of the Paleozoic Era - the Ordovician Period - began with the evolution of the first land plants, the mosses, sometime around 472 million years ago (sometime between December 18 or 19 on the Cosmic Calendar). This occurred along with the evolution of the first, primitive crustaceans (513 million years ago) that were the ancestors of all modern, terrestrial arthropods and insects. Terrestrial invertebrates and arthropods moved onshore about 450 million years ago (on or about December 19) and lived in a world where the land was covered entirely by bacteria, fungi, lichens, and mosses. Primitive insects lived near water or very moist environments where they could lay their eggs.

At the beginning of the next period of the Paleozoic Era, the Silurian Period, the first bony fish evolved about 440 million years ago, evolving bony jaws by about 420 million years ago.[21] The first vascular plants, the ferns, appeared on land about 415 million years ago (on or about December 20 of the Cosmic Calendar).

The next period of geologic time, the Carboniferous Period of the Paleozoic Era, began when the first amphibian tetrapods evolved from the ancestors of fleshy-finned lung fish about 360 million years ago (sometime between December 21 or 22 of the Cosmic Calendar). Amphibians, which need a very moist, wet environment in which to survive, eventually evolved thicker skins and the ability to lay their eggs with leathery shells that wouldn't dry out in a drier, terrestrial environment. The first reptiles evolved from these amphibian ancestors about 330 million years ago (sometime between December 22 or 23). The first seed-bearing plants also appeared during this period, about 320 million years ago, resulting in the first swampy "fern forests."

The Permian Period began about 300 million years ago (on or about December 23 of the Cosmic Calendar) when the conifers appear and spawned the great "Carboniferous Forests" of giant redwoods and other evergreen trees, lush with ferns and moss in a very warm, moist, tropical environment that existed over most of the earth at that time. It was these forests that became the great deposits of coal and oil that have been exploited by humans for the last 400 years in enormous quantities. There were not yet any flowers in the ancient forests. The Permian Period is the last period of the Paleozic Era.

The first period of the Mesozoic Era, the Triassic Period, began about 250 million years ago. The Triassic began in the wake of the Permian–Triassic extinction event, which left the Earth's biosphere impoverished; it would take well into the middle of the period for life to recover its former diversity. Two early groups of reptile ancestors, the therapsids (ancestors to the mammals) and archosaurs (ancestors to the dinosaurs and, later, the birds), were the chief terrestrial vertebrates during this time. A specialized subgroup of archosaurs, the dinosaurs, first appeared in the Late Triassic but did not become dominant until the succeeding Jurassic. The first true mammals, themselves a specialized subgroup of therapsids, also evolved during this period from egg-laying descendants of the dinosaurs that had developed the ability to regulate their internal body temperature and grow hair.

Also evolving during the Triassic were the first flying vertebrates, the pterosaurs, who like the dinosaurs were a specialized subgroup of archosaurs. The vast supercontinent of Pangaea existed until the mid-Triassic, after which it began to gradually rift into two separate landmasses, Laurasia to the north and Gondwana to the south. The global climate during the Triassic was mostly hot and dry, with deserts spanning much of Pangaea's interior. However, the climate shifted and became more humid as Pangaea began to drift apart. The end of the period was marked by yet another major mass extinction, wiping out many groups and allowing dinosaurs to assume dominance in the Jurassic.

By about 200 million years ago (on or about December 26 of the Cosmic Calendar), the beginning of the Jurassic Period of the Mesozoic Era, some of the descendants of the reptilian archosaurs had become very large and dominated the Earth's ecosystems during the "Age of the Dinosaurs." Also at the beginning of the Jurassic, very small, egg laying mammals (the monotremes) had already evolved (about 210 million years ago). This class of animals had the advantage of vascular body temperature regulation, a four-chambered heart and, later, conceived living young, rather than laying more vulnerable eggs.

Mammals were also distinguishable by the fact that they possessed limbs that articulated directly under the torso, which allowed for greater mobility and speed of movement. Also, unlike the reptiles, mammals grew hair, which enhanced their ability to regulate their internal body temperature independent of environmental temperatures, as well as developing a more complex middle ear,[22] which enhanced the ability to hear sounds. About the time birds first evolved, a subgroup of mammals (the therians) began giving birth to live young, the mothering of which also promoted the development of primitive social habits not commonly found (although not entirely absent) among reptiles. Although birds also lay eggs and do not give birth to live young, their young are born helpless, like mammals, and require an extended period of care by the parents, also facilitating social behaviors. Birds evolved directly from a subgroup of dinosaurs, the archosaurs, about 160 million years ago (late on December 27).

About 140 million years ago (around 7:30 a.m. on December 28 of the Cosmic Calendar), at the beginning of the last period of the Mesozoic Era - the Cretaceous Period - the first flowering plants had evolved. About 105 million years ago, Africa separated from the other continents causing a divergence of the Afrotherians (golden moles, elephant shrews, tenrecs, aardvarks, hyraxes, elephants and sea cows) from the other mammals. About 90 million years ago, the Boreoeutherians (all other modern mammals except the Marsupials and New World Xenarthrans) evolve, some of whom, including the common ancestor of the shrews, lemurs, and primates returns to the African continent. About 80 million years ago (on or about 9:30 p.m. on December 29), the first primates (tarsier-like mammals) had evolved somewhere on the African continent and coexisted with the dinosaurs.

Sometime between 66 and 65 million years ago (sometime between 6:15 and 6:50 a.m. on December 30), the Earth collided with a very large asteroid in the vicinity of the Caribbean just north of the Yucatan Peninsula, causing enormous amounts of dust to be ejected into the atmosphere and a drastic, severe cooling in the Earth's overall climate. This huge climactic change precipitated the Cretaceous-Triassic (K-T) Extinction event that wiped out the dinosaurs and allowed mammals to become the dominant form of terrestrial, vertebrate life, due to their better ability to adapt to dramatically cooler climactic conditions. Along with the mammals, and because of their own ability to adapt and survive, birds are considered by some to be the only "dinosaurs" to survive the K-T Extinction. The K-T Extinction marks the boundary between the preceeding Mesozoic Era and the succeeding Cenozoic Era, in which we now live.

The Cenozoic Era

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After the Cretaceous-Tertiary (K-T) Extinction (about 6:50 a.m. on December 30 of the Cosmic Calendar) came the Paleogene Period of the Cenozoic Era, which lasted from about 66 million to 23 million years ago. This period is most notable as being the time in which mammals evolved from relatively small, simple forms into a large group of diverse animals in the wake of the Cretaceous–Tertiary Extinction event that ended the preceding Cretaceous Period. Some of these mammals would evolve into large forms that would dominate the land, while others would become capable of living in marine, specialized terrestrial, and even airborne environments. Birds also evolved considerably during this period, changing into roughly modern forms. Most other branches of life on earth remained relatively unchanged in comparison to birds and mammals during this period. Some continental motion took place. Climates cooled somewhat over the duration of the Paleogene and inland seas retreated from North America early in the period.

The Paleogene Period is composed of the Paleocene, Eocene, and Oligocene Epochs. Terrestrial Paleocene strata immediately overlying the K-T boundary is in places marked by a "fern spike": a bed especially rich in fern fossils. Ferns are often the first species to colonize areas damaged by forest fires. Thus, the fern spike may indicate post-Chicxulub crater devastation caused by the asteroid impact that caused the K-T extinction.

In general, the Paleocene Epoch is marked by the development of modern plant species. Cacti and palm trees appeared. Paleocene and later plant fossils are generally attributed to modern genera or to closely related taxa. The warm temperatures worldwide gave rise to thick tropical, sub-tropical and deciduous forest cover around the globe (the first recognizably modern rain forests), with ice-free polar regions covered with coniferous and deciduous trees. With no large, grazing dinosaurs to thin them, Paleocene forests were probably denser than those of the Cretaceous. Flowering plants (angiosperms), first seen in the Cretaceous, continued to develop and proliferate and, along with them, coevolved the insects that fed on these plants and pollinated them.

The end of the Paleocene Epoch, about 55 million years ago (at about 1:10 p.m. on December 30 of the Cosmic Calendar), was marked by one of the most significant periods of global change during the Cenozoic - a sudden global change, the Paleocene-Eocene Thermal Maximum - which upset oceanic and atmospheric circulation and led to the extinction of numerous deep-sea benthic foraminifera and, on land, a major turnover in mammals.

The Eocene Epoch of the Paleogene Period, of the Cenozoic Era, which succeeded the Paleocene Epoch of that same period and era, is notable in the evolution of human beings for the first appearance of the simians - monkey-like primates - about 45 million years ago (at about 7:30 p.m. on December 30 of the Cosmic Calendar), with the first true monkeys evolving about 40 million years ago (10:40 p.m.). Most other modern animal genera, including the carnivores and cetaceans, also evolved during this period.

The final epoch of the Paleogene Period, the Oligocene Epoch, began about 34 million years ago (on or about 1:50 a.m. on December 31 of the Cosmic Calendar) and is known for its sparsity of additional, modern mammalian faunas after a burst of evolution during the Eocene. The start of the Oligocene is marked by a major extinction event: a faunal replacement of European with Asian fauna, except for the endemic rodent and marsupial families, called the Grande Coupure. At the beginning of the Oligocene, the New World Monkeys somehow migrate from Africa to the New World on either vegetable rafts or over a land bridge. The Oligocene-Miocene boundary is not set at an easily identified worldwide event but rather at regional boundaries between the warmer late Oligocene and the relatively cooler Miocene. By the end of the Oligocene, about 23 million years ago, the ancestor of all apes has diverged from the Old World monkeys.

Angiosperms continued their expansion throughout the world, with tropical and sub-tropical forests replaced by temperate, deciduous woodlands. Open plains and deserts became more common. Grasses expanded from their water-bank habitats in the Eocene and moved out into open tracts. However, even at the end of this period, grasses were not quite common enough for the emergence of modern savanna. In North America, subtropical species dominated, with cashews and lychee trees present and temperate trees such as roses, beech and pine common. The legumes of the pea and bean family spread, and sedges, bulrushes and ferns continued their ascent.

During the next period of the Cenozoic Era to follow the Paleogene Period, the Neogene Period (beginning about 23 million years ago, on or about 9:25 a.m. of December 31 of the Cosmic Calendar) saw a considerable evolution of bird and mammal species, whereas most other plant and animal forms went relatively unchanged. Some continental motion took place, the most significant event being the connection of North and South America in the late Pliocene, permitting an exchange of species over the Isthmus of Panama. Climates cooled somewhat over the duration of the Neogene, culminating in continental glaciations in the last period of the Cenozoic Era - the Quaternary Period - in which we now live and that witnessed the dawn of the genus Homo.

The Neogene Period is composed of two epochs: the Miocene and Pliocene Epochs. During the Miocene Epoch, which lasted until 5.3 million years ago, grasslands underwent a major expansion and forests fell victim to a generally cooler and drier climate overall. Grasses also diversified greatly, co-evolving with large herbivores and grazers, including ruminants. At the beginning of this epoch, the ancestor of all apes had diverged from the Old World monkeys. At about 18 million years ago (about 12:35 p.m.), ancestors of the gibbons (the "lesser apes") had diverged from the other hominoids and, by about 14 million years ago (3:10 p.m.), ancestors of the orangutans (the first of the "great apes") had diverged from the other hominins.

Both marine and continental fauna were fairly modern at this time, although marine mammals were less numerous. Only in isolated South America and Australia did widely divergent fauna exist. In the Early Miocene, several Oligocene groups were still diverse, including nimravids, entelodonts, and three-toed horses. Like in the previous Oligocene Epoch, oreodonts were still diverse, only to disappear in the earliest Pliocene.

During the later Miocene, mammals were more modern, with recognizable dogs, raccoons, horses, beaver, deer, camels, and whales, along with now extinct groups like borophagine dogs, gomphotheres, and semi-aquatic and hornless rhinos like Teleoceras and Aphelops. Islands began to form between South and North America in the Late Miocene, allowing ground sloths like Thinobadistes to island-hop to North America.

Unequivocally recognizable dabbling ducks, plovers, typical owls, cockatoos and crows appeared during the Miocene. By the epoch's end, all or almost all modern bird families are believed to have been present; the few post-Miocene bird fossils which cannot be placed in the evolutionary tree with full confidence are simply too badly preserved instead of too equivocal in character.

Marine birds reached their highest diversity ever in the course of this epoch. Brown algae, called kelp, proliferated, supporting new species of sea life, including otters, fish and various invertebrates. The cetaceans diversified, and some modern genera appeared, such as the sperm whales. The pinnipeds, which appeared near the end of the Oligocene, became more aquatic.

Approximately 100 species of apes lived during this time. They ranged over much of the Old World and varied widely in size, diet, and anatomy. Due to scanty fossil evidence, it is unclear which ape or apes contributed to the modern hominid clade (which includes the Orangutans), but molecular evidence indicates this ape lived somewhere between 15 to 12 million years ago (sometime between 2:30 p.m. and 4:25 p.m. on December 31 of the Cosmic Calendar).

In the oceans, modern sharks appeared at this time, including the huge Megalodon. Marine crocodiles and birds, like the plotopterids and Gavialosuchus, shared the seas with marine mammals like desmostylians, dugongs like Metaxytherium, and whales, which ranged from forms similar to the ones present today to the cetotheres and the long-beaked dolphin Pomatodelphis.

Between 7 and 6 million years ago (between 7:35 and 8:10 p.m. on December 31), there occurred a sudden expansion of grasses which were able to assimilate carbon dioxide more efficiently but were also richer in silica, causing a worldwide extinction of large herbivores. The expansion of grasslands and radiation of species among terrestrial herbivores such as horses can be linked to fluctuations in the greenhouse gas, carbon dioxide. This climatic change is also believed to be responsible for the divergence of gorillas from the other hominins at about this time. The first recognizably "human-looking" hominins, the Australopithecines, diverged from their common ancestor with the Chimpanzees at the end of the Miocene, about 5.4 million years ago (at about 8:35 p.m. on December 31 of the Cosmic Calendar). Present scientific consensus holds that the Genus Homo descended directly from an Australopithecine ancestor.

The last epoch of the Neogene Period, the Pliocene, lasted from about 5.3 million (8:40 p.m.) to 2.6 million (10:20 p.m.) years ago. It was during this time that the common link between the ancestors of the other great apes and human beings evolved. The change to a cooler, dry, seasonal climate had considerable impacts on Pliocene vegetation, reducing tropical species worldwide. Deciduous forests proliferated, coniferous forests and tundra covered much of the North, and grasslands spread on all continents (except Antarctica). Tropical forests were limited to a tight band around the Equator and, in addition to dry savannahs, deserts appeared in Asia and Africa.

Both marine and continental faunas were essentially modern, although continental faunas were a bit more primitive than today. The first true human beings, Homo Habilis, appeared at the end of the Pliocene. The land mass collisions meant a greater migration and mixing of previously isolated species, such as in the Great American Interchange. Herbivores got bigger, as did specialized predators.

Evolution of the Hominins

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In regard to the common link between the ancestors of gorillas and humans, human kind's first hominini ancestor with the gorillas diverged from their common ancestor sometime between eight and seven million years ago and began to travel larger distances between trees due to a dramatic climactic change to a warmer and more arid climate. The earliest known candidate for hominini status is Sahelanthropus Tchadensis, who lived approximately seven to six million years ago. Although she could walk mostly upright on two feet over larger distances than other apes, Sahelanthropus lived more in the trees than on the ground.

Living sometime between 6.2 and 5.8 million years ago, Orrorin Tugenensis was another candidate for complete divergence of humans from their common ancestor with the other extinct proto-human species. Due to certain anatomical characteristics, if divergence at this point had proved to be true then Australopithecus (see below) would have been considered a side branch and not the direct ancestor of human beings. However, due to the equivocal nature of some of the evidence of human-like anatomy, as well as the paucity of the archaeological record for this species relative to the abundance of finds for Ardipithecus and Australopithecus, this hypothesis is not widely accepted among anthropologists.

First evolving about 5.8 million years ago, and walking nearly fully upright, the Ardipithecines were very clearly divergent from their common ancestor with the chimpanzees. With opposable first toes, Ardipithecines still spent much of their time climbing about in trees. Eventually, Austrolopithecus (see below), an offshoot of Ardipithecus, eschewed life in the trees. The Ardipithecus genus eventually became extinct about 4.4 million years ago.

About 4.2 million years ago (at about 9:20 p.m. on December 31 of the Cosmic Calendar), the immediate ancestor genus of Homo, Australopithecus, first appeared. Walking upright had gradually caused the pelvic girdle to evolve more vertically, causing Australopithecine young to be born prematurely relative to other great apes, which have a gestation period of about one year. Premature birth led to a greater plasticity of neural development and a greater ability to learn new skills. Premature young required greater, early post-natal care which resulted in selective pressures favoring the development of a greater intellectual capacity for culture and increased intelligence.

These primates no longer had opposable first toes and no longer lived an arboreal existence. Walking upright also meant that less opposable thumbs were not as important for grasping tree limbs and branches. Consequently, the thumbs of these primates grew longer until they became fully opposable, allowing for the better grasping and manipulation of tools. Recently discovered evidence of stone tool use dating as far back as 3.4 million years indicates that Australopithecus was a probable stone tool user, although no finds indicate that Austrolopithecus actually manufactured stone tools. The Australopithecines became extinct about 2.1 million years ago.

About 2.4 million years ago (at about 10:30 p.m.), the first truly "human" genus, Homo Habilis ("handy man") had evolved, marking the end of the Neogene Period and the beginning of the last period of the Cenozoic Era, the Quaternary Period. The Quaternary Period itself is composed of three epochs: the Pleistocene, the Holocene, and the Anthropocene. The Pleistocene Epoch, also known as the "Stone Age," lasted until about 11,000 years ago, about three thousand years after the end of the last Ice Age. The Holocene Epoch that followed lasted until about 1750 CE, when the large-scale emission of greenhouse gasses began to dramatically warm the Earth's atmosphere and ushered in the final epoch of the Quaternary Period, the Anthropocene. Large scale impacts by human beings on the Earth's environment have, at this time, commenced the Earth's Sixth Great Extinction event and the probable end of the Quaternary Period, as well as possibly the end of the Cenozoic Era - the final era of the Phanerozoic Eon - depending on how dramatically the environment and ecosystem are altered by human intervention.

Beginnning with Homo Habilis, fully opposable thumbs and enhanced intelligence permitted human kind's ancestors to make and use crude rock tools of the Oldowan Technology type. This also marked the beginning of the first major period of human cultural development - the Paleolithic. Thus, by definition, the first use of manufactured tools marks the evolution of human being's genus (Homo) and of our first ancestor species (Homo Habilis).

The usefulness of tools and the culture needed to transmit their knowledge further favored the development of increased intelligence. Increased intelligence meant a greater plasticity of neural development in the brain and an even longer period of childhood and adolescence, further enhancing cultural development. A change from eating grasses, sapling strips, and tubers to a more omnivorous diet (made possible by tool use) caused the jaw muscles to weaken, thereby allowing the cranium of the skull to expand and accommodate a larger brain. A higher protein diet, made possible by the introduction of animal meat, enhanced development of the brain during adolescence. H. Habilis became extinct about 1.4 million years ago.

The species Homo Erectus first appeared about 1.9 million years ago (at about 10:50 p.m. on December 31 of the Cosmic Calendar) and constituted a probable ancestor of modern humans (Homo Sapiens). Homo Erectus most likely originated in Africa, though Eurasia cannot be ruled out. Regardless of where she first evolved, this species seems to have dispersed quickly, starting about 1.7 million years ago (at about 10:55 p.m.), near the middle of the Pleistocene Epoch, and moving through the African tropics, Europe, South Asia, and Southeast Asia. This history has been recorded directly, if imprecisely, by many sites that have yielded fossil remains of H. Erectus. At other localities, broken animal bones and stone tools have indicated the presence of the species, though there are no traces of the people themselves.

H. Erectus was a human of medium stature that walked upright. His braincase was low, the forehead was receded, and the nose, jaws, and palate were wide. The brain was smaller and the teeth larger than in modern humans. H. Erectus seems to have flourished until about 143 thousand years ago, before giving way to Homo Sapiens.

A somewhat later human species to evolve, Homo Ergaster, lived about 1700 to 200 thousand years ago (beginning by about 11:33 p.m. of December 31 of the Cosmic Calendar). This hominin used the first standardized stone tool technology, Acheulean Technology, and the first, coordinated, hunter-gatherer groups. This industry involved the chipping of axe heads and scraping tools. Crude bone and antler tools might have also been used. This is evidence of a very primitive, human culture. Depictions of humans from this period using spears to hunt animals are generally exaggerating the technological development of these people as the spear was not developed, if at all, until very late in this period. Homo Ergaster's remains are found throughout Asia, as well as Africa, but not in Europe.

Another species of human, Homo Heidelbergensis, lived about 700 to 200 thousand years ago. It is at the beginning of his time that we see the first relatively certain widespread use of controlled fires and natural shelters, making H. Heidelbergensis the first "cave man."

At some point during the time of Heidelbergensis, human kind's ancestors probably began using some sort of proto-language, comprised mainly of gestures and emotive sounds; a fully symbolic use of language was not utilized until much later, about 100,000 years ago (11:56 p.m. on December 31 of the Cosmic Calendar). Hominins now occupied the entire Old World, including Europe.

Although previously controversial, some anthropologists now hypothesize that a new species, Homo Antecessor, is the probable ancestor of Homo Sapiens whereas, previously, Homo Heidelbergensis was claimed to be the probable ancestor of Homo Neanderthalensis ("Neanderthal Man") and that Neanderthal was therefore a species entirely separate from Homo Sapiens. The anthropologists who now hypothesize the existence of Antecessor believe that the human genome for non-African ancestors contains many Neanderthal genes, which they claimed indicates that matings of Homo Sapiens and Neanderthals occurred that produced fertile offspring. This hypothesis has since been proven correct based on the gene sequencing of teeth from the remains of archeological digs. Although the issue of speciation remains controversial, some anthropologists now consider Neanderthal to be the same species as Homo Sapiens[23] and those scientists would find the proper designations for the two subspecies to be Homo Sapiens Neanderthalensis and Homo Sapiens Sapiens, both descending directly from Homo Antecessor, not Homo Heidelbergensis.

Human Cultural Evolution During the Pleistocene ("Stone Age")

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Approximately 200,000 years ago (at 30 seconds after 11:52 p.m. on December 31 of the Cosmic Calendar), anatomically modern humans (Homo Sapiens akin to the later Cro-Magnon) had evolved somewhere in Equatorial East Africa. Mitochondrial Eve, the common ancestor of all humans living today, was born sometime near the beginning of this period. Homo Sapiens are the only surviving species of the Homo genus extant today.

At this time, the first signs of something approaching "modern" human culture began to appear. More sophisticated stone tools were made by striking flakes from a flint core in alternating directions; used cores were later used as choppers. Flakes were trimmed and used as scrapers or knives. A kind of concave scraper, perhaps used to smooth and shape wooden spears, was typical of this Clactonian industry. Many different types of hand axes were made, as well as the first borers, knives, and spears. Heavily serrated, stone blades were sawlike, allowing them to be used for carving and cutting horn, bone, and wood.

Sometime between 160,000 and 135,000 years ago, some mitochondrial L0 haploid-bearing human groups migrated out of East Africa and into South Africa. Sometime soon afterward, Haplogroup L1 migrated to Central and West Sub-Saharan Africa, some of whom later became the ancestors of the modern Pygmies. Remnants of pure L0 and L1 haplogroups remain in East Africa today.

Sometime between 135,000 and 115,000 years ago, some L2 haploid-bearing Homo Sapiens migrated out of the Niger-Congo region and into most of North-Central Sub-Saharan Africa and eventually crossed into the region of the Levant (the first group descending from Mitochondrial Eve to leave the African continent). Prior to this time, inhabited sites are generally random scatterings of refuse of various kinds. In the dwelling areas of behaviorally modern, early Homo Sapiens, on the other hand, there is a definite pattern in the use of space - i.e., tool-making was done in one place, cooking in another, sleeping elsewhere. The earliest signs of such partitioning are found at the South African site of the Klasies River Mouth, dating to more than 100,000 years ago.

Sometime near the end of this period, another L haploid group, L3, appeared somewhere in the Horn of Africa. L3 crossed the Red Sea into the region of the Saudi Arabian Peninsula now known as Yemen and became the group of African emigres that would constitute the ancestors of all non-African groups, as well as African groups north of the Sahara, that later developed. By 90,000 years ago, an ice age turned the Levant and Saharan Africa into desert and the L2 group vanished. The region populated by L2 was later repopulated by Neanderthals. Sometime during this period, humans were using a fully symbolic language for communication.

About 74,000 years ago, the super-eruption of Mt. Toba commenced a 1,000 year ice age that depopulated South Asia to less than 10,000 individuals. Over the next 10,000 years, South Asia was repopulated by groups surviving in Southeast Asia. This population "bottle neck" may explain why genetic biodiversity in Africa is much greater than in the rest of the world, despite morphological differences due to superficial racial characteristics. Groups in Africa continued to be somewhat isolated from each other and thereby maintained their genetic differences, whereas the "bottle neck" created a much smaller gene pool in the Middle East and Southern Asia, from which all later, non-African humans ultimately descended.

Between 70,000 and 60,000 years ago, the M Haplogroup descended from L3 and appeared somewhere between East Africa and South-Central Asia. One group moved through Southern Asia into Southeast Asia, and into Australia by about 45,000 B.C.E. (becoming the ancestors of the present-day Australian Aborigines). Another group moved northward into Siberia and Eastern Asia, with some moving South again and into Southeast Asia sometime between 40,000 and 35,000 B.C.E.

Sometime between 65,000 and 52,000 years ago (at 30 seconds about 11:57 p.m. on December 31 of the Cosmic Calendar), another descendant of L3, the N Haplogroup, moved (possibly) across the Sinai Peninsula, then throughout Asia, into Oceania and Australia, much later into the Americas (either from Oceania and/or across the Bearing Straight), and also later into Europe, becoming the most widespread genetic clade. Descending from the N group, Haplogroup R emerged in South Asia and spread throughout Southwest Asia and West Eurasia, where it is most prominent. A little later, between 52,000 and 45,000 years ago, Haplogroup U descended from group R in West Eurasia and spread into Europe, North Africa, the Middle East, India and the Caucasus. This haplogroup is the progenitor of all modern Indo-European groups.

During this period, Mousterian Technology predominated throughout the Old World North of Sub-Saharan Africa. Tools used by both Neanderthals and modern Homo Sapiens included small hand axes made from disk-shaped cores; flake tools, such as well-made sidescrapers and triangular points, probably used as knives; denticulate (toothed) instruments produced by making notches in a flake, perhaps used as saws or shaft straighteners; and round limestone balls, believed to have served as bolas (weapons of a type used today in South America, consisting of three balls on the end of a thong, which is hurled at an animal, wraps itself around its legs, and trips it).

Homo Sapiens were now living in fully-developed, human, hunter-gatherer communities. Humans were distilling and mining Salt (sodium chloride with a small amount of potassium chloride present) and were using the salt to cure meats and preserve foods. Homo Sapiens also used Potash as a bleaching agent and oil lamps were used for lighting. This is the period of Aurignacian Culture, with the oldest known example of figurative art, the ivory Venus of Hohle Fels, coming from this culture. Many archaeologists have doubted that Neanderthals used any of the aforementioned chemical or advanced lighting technologies, although this skepticism is being currently challenged. Around 40,000 years ago, Haplogroup R0 descended from group R on the Arabian Peninsula and moved into Central Asia, becoming the progenitor of all modern Central Asian peoples.

Between 35,000 and 21,000 years ago (at about 11:59 p.m. on December 31 of the Cosmic Calendar), three or four different species of the Homo genus coexisted: Homo Sapiens, Homo Denisova, Homo Floresiensis (the so-called "hobbit" man), and maybe Homo Neanderthalensis, but only if they are considered a species apart from Homo Sapiens. The latter species eventually became extinct during this period due to competition from Homo Sapiens. It is also during this period that the last ice age (the Wisconsin Glacial Stage) began to end, resulting in the desertification of regions in the lower latitudes and the development of more modern human cultures in the more northern, wetter, latitudes. The retreat of the glaciers also permitted humans to cross the Alaska-Siberia land bridge, thus permitting their population of the New World. That land bridge vanished sometime about 12,000 years ago due to rising ocean levels. The bridge between the British Isles and Western Europe vanished due to rising sea levels about 4,000 to 5,000 years after that.

At the beginning of this period, Haplogroup H descended from Group R0 in the region of the Caucasus. Sometime after 30,000 B.C.E., Group H moved, along with Haplogroup I from the same region but descended directly from Group N, as the second migration of humans into Western Europe (after Haplogroup U), probably as Cro-Magnon Man, sometime between 25,000 and 20,000 BCE. This would make their arrival roughly contemporaneous with the emergence of Perigordian Culture, which replaced the Aurignacian Culture.

The first evidence of counting on bone or stone appeared at the beginning of this period. Small, pointed, restruck blades with a blunt but straight back, a carving tool known as a Noailles burin (a woodworking tool rather like a chisel), were developed, as well as arrowheads used on spears for big game hunting. People in the Perigordian period also used nets to hunt small game. Artistic achievements of the Gravettian Cultural stage included hundreds of the very familiar, clay "Venus" figurines, which constitute the earliest known use of clay, in this case for sculpting. It is also during this period that Neanderthals and the other Homo species are outcompeted to extinction by Homo Sapiens.

About 25,000 to 15,000 years ago, Haplogroups A and B, descended from Haplogroups N and R respectively, and constituted the first migration of peoples into the New World continents, ultimately occupying primarily the Eastern halves of North and South America as they became displaced by later-arriving groups. Humans were now found on every continent, except Antarctica.

During this time, Solutrean Culture flourished in what would become Southwestern France and then spread throughout the European Sub-continent, replacing the Perigordian Culture in that region. The Solutrean presages the development of the Magdalenean Culture in Southwest Europe - a cultural high-point for early humans that subsequently influenced the rest of human cultural development throughout the world. During the Solutrean, a variety of tools such as burins, scrapers, and borers continued to be used; but blades that were formed in the shape of laurel or willow leaves and shouldered points are the implements that distinguished the Solutrean. During this period, the earliest known use of clay for making ceramic pottery occurred.

About 17,000 years ago (39 seconds before the end of the Cosmic Calendar), the Magdalenian Culture of Southwestern Europe appeared, replacing the Solutrean and Perigordian Cultures, and continued until about 11,000 year ago (25 seconds before the end of the Cosmic Calendar), when it was generally replaced and succeeded by the simplified Azilian Culture. As such, the Magdalenian Culture represented the culmination of Upper Paleolithic cultural development in Europe. During this time, Proto-Afroasiatic, a language from which all other North African and Semitic languages descend, was spoken somewhere in the Middle East.

The Magdalenians lived at a time when reindeer, wild horses, and bison formed large herds; the people appeared to have lived a semisettled life surrounded by abundant food. They killed animals with spears, snares, and traps and lived in caves, rock shelters, or substantial dwellings in winter and in tents in summer. The great increase in art and decorative forms indicates the Magdalenians had leisure time. They also experienced a population explosion, living in riverside villages of 400 to 600 persons. It has been estimated that the population of what would become France increased from about 15,000 persons in Solutrean times to over 50,000 in Magdalenian times.

Magdalenian stone tools included small geometrically shaped implements (e.g., triangles, semilunar blades) probably set into bone or antler handles for use as burins, scrapers, borers, backed bladelets, as well as shouldered and leaf-shaped projectile points. Bone was used extensively to make wedges, adzes, hammers, spearheads with link shafts, barbed points and harpoons, eyed needles, jewelry, and hooked rods probably used as spear throwers. Bone tools were often engraved with animal images.

Magdalenian culture disappeared as the cool, near-glacial climate warmed at the end of the Fourth (Würm) Glacial Period (c. 10,000 BCE), and herd animals became scarce. It has been suggested that the complexity of the later cave art represents an attempt by Magdalenian man using “sympathetic magic” to cause the animals to once more become abundant. The Azilian culture, which followed the Magdalenian, was much simplified, and there is a poverty of art. Clearly the richness of Magdalenian culture owes much to the abundance of food, allowing time for leisure and the development of religion and aesthetics. About 13,600 years ago, Haplogroup V originated in the Franco-Cantabrian Region of Europe and spread throughout Western Europe, as far as Scandinavia, and into North Africa.

Around 15,000 to 12,500 years ago, descendants of Haplogroup M (which are Haplogroups C and D) and of Haplogroup N (which is Haplogroup X) moved from Siberia and across the Arctic land bridge into Northern-most North America and, eventually, into the rest of the Western Americas, becoming the second wave of migration of peoples later called the "Native Americans." At an unknown later date, but probably after the disappearance of the Bering Straight land bridge due to rising sea levels, the ancestors of the Aleut peoples populated the Arctic and became the third and final wave of peoples to populate the New World prior to the arrival of Europeans in the late fifteenth and sixteenth centuries CE.

Around 12,500 years ago, the Jomon Culture began in Japan, with the use of pottery, fishing, hunting, and gathering acorns, nuts and edible seeds. There are 10,000 known sites. This culture continued with relatively little change until around 300 BCE, when it was replaced by the Yayoi Culture, probably due to contact with more advanced asian continental cultures.

About 11,700 years ago (9700 BCE), the Azilian Culture in Spain and Southern France, and the Sauveterrian Culture in Northern France and Central Europe, began to replace the Magdalenian Culture. Depending on the region, this development represents the earliest end of the Paleolithic Period of human culture and the beginning of the Mesolithic. These tool traditions later evolved into such local industries as the Tardenoisian (Northern France and Central Europe), Maglemosian (Nordic), Ertebølle (Danish and German), and Asturian (Southern France and Spain) in other regions of Europe. The development of the Azilian and Sauveterrian cultures also represents the conventional end of the Neogene Period and the beginning of the Holocene Period, in the most recent Quaternary Period of the Cenozoic Era of the geologic time-scale.

Stone tools of the Azilian and Sauveterrian Cultures were mostly extremely small, called microliths, and were made to fit into a handle of bone or antler. Projectile points with curved backs and end scrapers were used; bone tools included punches, “wands” (of uncertain use), and flat harpoons often made of red-deer antler. Art was confined to geometric drawings made on pebbles using red and black pigments. The big game of the Fourth Glacial Period, known as the Würm Period, had disappeared or been hunted to extinction, and the Azilian and Sauveterrian peoples and their contemporaries ate mollusks, fish, birds, and small mammals that were probably trapped and snared. Also during this time, the Maglemosian peoples inhabited the settlements of Star Carr, in Yorkshire, and Cramond, in Scotland. At this time, humans began to repopulate the post-glacial Nordic region.

At the same time, a mesolithic culture of Palestine and Southern Syria appeared, dating from about 9000 BCE (25 seconds before the end of the Cosmic Calendar). Mainly hunters, the Natufians of this region supplemented their diet by gathering wild grain; they likely did not cultivate it. They had sickles of flint blades set in straight bone handles for harvesting grain and stone mortars and pestles for grinding it. Some groups lived in caves, others occupied incipient villages. They buried their dead with their personal ornaments in cemeteries. Carved bone and stone artwork have been found. At this time, semitic groups remigrated back into North Africa as the ancestors of the Egyptians, Berbers, and others, and the earliest evidence of building with stone is found at Jericho. Also, at the beginning of this period, animal domestication, including beekeeping, is accomplished and the repeated and regular foraging of certain locations for seed-bearing grasses began to develop into routine cultivation about this time. Proto-Chadic, Proto-Egyptian, and Proto-Omotic are spoken somewhere in North Africa.

Human Cultural Evolution During the Neolithic and Agricultural Revolutions (7000 - 3000 BCE)

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Due to the advent of irrigation about 7000 BCE (21 seconds before the end of the Cosmic Calendar), which was necessary to permit agriculture in the lower latitudes and more arid regions of the world, the neolithic culture and the so-called "agricultural revolution" spread throughout Eurasia and China. Until this time, agriculture was relegated to northern climes, which later introduced this technology to the Middle East and North Africa. However, true "civilization"[24] did not come into existence until the lower latitude peoples (probably under the tutelage of a priestly class) organized themselves well enough to irrigate their lands.

The malting of grain and beer-making probably first happened sometime during this period. Naturally occurring sulfur compounds were used in medications and as agricultural fumigants. The first town settlements and domestication of animals occurred in the Middle East. Mud bricks were used for building and plant fibers were spun into thread for sewing and, eventually, weaving.

The sites of Xianrendong in Jiangxi and Zengpiyan in Guangxi have yielded artifacts from the 10th to the 7th millennia BCE that include low-fired, cord-marked shards with some incised decoration and mostly chipped stone tools. The pots found may have been used for cooking and storage. Pottery and stone tools from shell middens in southern China also suggest incipient Neolithic occupations. These early southern sites may have been related to the Neolithic Bac Son culture in Vietnam. Connections to the subsequent Neolithic cultures of northwestern and northern China have yet to be demonstrated.

From about 8000 to 6000 BCE, both Haplogroup J (from the Caucasus) and Haplogroup T (from Mesopotamia and the Eastern Mediterranean) moved into Western Europe, representing the third great migration of humans into Europe. These migrations brought a more settled lifestyle (pastoralism and then settled agriculture) to the earlier European hunter-gatherer cultures already living there. Displaced groups migrated northward into Scandinavia and Russia, eventually becoming the Germanic and Nordic peoples.

By the beginning of this period, a pattern of settled lifestyle was found throughout the Old World north of Sub-Saharan Africa. At some point during this time, the population of human beings on the Earth exceeds five million for the first time. We see the earliest evidence of clay bricks used for building at Jericho and unfired, clay pottery sees widespread use. The domestication of the bottle gourd provides a useful technology for storing and transporting liquids without the use of heavier and more fragile ceramic pottery.

By 6500 BCE (20 seconds before the end of the Cosmic Calendar), the Neolithic period of human cultural development is ending in the Middle East and the earliest "metal age" cultures emerged with the large-scale smelting of lead beads, produced in the region that is now Turkey but which has been historically called Anatolia. Silver, tin, copper, zinc and various arsenic and antimony compounds were probably separated from the same ore as the lead. The large-scale smelting of copper (not earlier than about 5000 BCE) throughout the Middle East ushered in the Chalcolithic Age (a period that developed in other regions at later times). The Chalcolithic Age coincided with the widespread appearance of larger-scale civilized communities in regions that had developed year-round, irrigated agriculture.

Large-scale ceramic industries without the use of a potter's wheel made their first appearance in the region of Anatolia about this time. These pots were most frequently made using a coiling technique (corded ware) and were hard-fired. Proto-Cushitic, an Afroasiatic language, was spoken somewhere in the Middle East and the agriculture of maize, beans, and squash developed in Meso-America.

At about this same time, an aceramic (i.e., lacking pottery) Neolithic occupation occurred in the region around the mouth of the Indus River and the Indo-Iranian Plateau. The main tools used there were stone blades, including lunates and triangles, some probably mounted in wooden hafts with bitumen mastic. However, only a relatively small number of ground stone axes have been found. Domestication of wheat and barley apparently reached the area sometime during this phase, as did that of sheep and goats, although the preponderance of gazelle bones among the animal remains suggests a continued dependence on hunting. Houses of mud brick in this region date from the beginning of this phase and continue throughout the occupation. Accompaniments to the simple burial of human remains included shell or stone-bead necklaces, baskets, and occasionally young caprids (both sheep and goats) slaughtered for the purpose. This level of cultural development does not find its way to the Northern Indus River Valley until around 3000 BCE.

Neolithic civilizations in the Northern Indus River and in the entire Ghanges River valleys were much more primitive than civilizations found earlier at the mouth of the Indus River and were characterized only by the emergence of pottery and minor improvements in agriculture. By the beginning of Phase 1B of the Mehrgarh Period I (7000 - 5500 BCE) of the Northern South Asian subcontinent, cattle (apparently Bos Indicus, the Indian humped variety) had come to predominate over game animals in the Northern Indus, as well as over sheep and goats. A new type of building, the small regular compartments of which identify it almost certainly as a granary, first appeared during this phase and became prevalent in Period II (5500 - 4800 BCE), indicating the frequent occurrence of crop surpluses.

Burial during the Mehrgarh Period I took a more elaborate form—a funerary chamber was dug at one end of a pit and, after inhumation, the chamber was sealed by a mud brick wall. From the latter phase of Period I also come the first small, hand-modeled female figurines of unburned clay. Granary structures proliferated, sometimes on a larger scale. The remains of several massive brick walls and platforms suggest something approaching monumental architecture. Evidence appears of several new crafts, including the first examples of the use of copper and ivory in this region. Areas of settlement appear to have grown to accommodate an increasing population.

At around 6000 BCE (18 seconds before the end of the Cosmic Calendar), the Hassuna, Hassuna-Sāmarrā, and Halaf cultures emerged in Northern Iraq. These were three periods of very early chalcolithic development, during which known early settlements were successively occupied by peoples who had relations with cultures in the regions of Syria and Anatolia. The designs on their pottery, sometimes in more than one color, usually consisted of zones filled with “geometric” ornament in patterns reminiscent of woven fabrics. These designs were often adapted to the shape of the vessels with creditable artifice. Only in Hassuna-Sāmarrā pottery do devices occasionally appear that consist of animal, bird, or even human figures, ingeniously stylized and aesthetically attractive. Such motifs, however, appeared to be adopted from contemporary Iranian ceramics.

The only other notable art form popular at this time in the Middle East is that of hominoid figurines of stone or clay, associated with primitive religious cults. However, their formal idiosyncrasies vary greatly from group to group, and the meaning of their symbolism is unknown. Neither can they — nor the pottery designs — be considered as ancestral to the Mesopotamian art of historical times, the antecedents of which must be sought in southern Iraq.

Within 250 years after the beginning of this period, the first settlements practicing intensive, irrigated, year-round agriculture emerged in Mesopotamia. Although agriculture probably found its origins in the well-watered North, irrigation and large-scale agriculture did not develop until the primitive agricultural technology was brought to the more arid regions of the South, which necessitated the more developed and advanced agricultural technologies.

At about this time in mainland East Asia, the Laoguantai Culture (in eastern and southern Shaanxi and northwestern Henan), Dadiwan I (a development of Laoguantai culture in eastern Gansu and western Shaanxi), and two other similar cultures, Peiligang (north-central Henan) and Cishan (southern Hebei) emerged, characterized by practiced agriculture, in the form of cultivating millet, and animal husbandry, in the form of raising pigs. Cishan culture is also one of the oldest in ancient China to make pottery on a large scale.

Ubaidian Culture developed (c. 5700 BCE) in the earliest known Mesopotamian city-state, Tall-al-Ubayd. This period is characterized by long successions of superimposed temples portraying the growth and development of an elaborate mud-brick architecture. No unquestionable instances of metal tools were available in southern Mesopotamia (although metal was available by that time in the north), but quantities of very highly fired clay tools (axes, adzes, sickles) have been found. These were useful for cutting the pithy woods, reeds, and grain of the southern alluvial environment or for dressing sun-baked bricks. The use of female clay figurines continued, but in a unique and highly characteristic stylization.

An Ubaidian town supplied itself from fields of wheat and barley and its animal herds. The agricultural regime in the hot, dry alluvium of southern Mesopotamia depended, however, upon the utilization of the braided lower channels of the Tigris and especially of the Euphrates. Though elaborate irrigation works did not exist, the management of even quite informal ditches, with necessary shifts when the natural channels of the rivers shifted, added a new dimension to the sociopolitical necessities of Ubaidian culture. This system of irrigation was probably one of the principal factors that contributed to the expansion of society in late prehistoric Mesopotamia.

At about 5500 BCE (17 seconds before the end of the Cosmic Calendar), the more advanced non-metalic technologies of the Middle East began to spread north and west over large areas of Europe, spreading from the region of the Danube River to present-day Slovakia and as far west as the Netherlands. This so-called "Danubian Expansion" encompassed a neolithic culture where farmers practiced a form of shifting cultivation on the loess soil. Emmer wheat and barley were grown, and domestic animals, usually cattle, were kept. The name LBK for this culture derives from an abbreviation of the German Linienbandkeramik, or Linearbandkeramik, a reference to the culture’s characteristic pottery, which was ornamented with pairs of parallel lines arranged in spiral or meander patterns. The most common stone tool was a polished stone adze. The people occupied large rectangular houses grouped in medium-sized village communities or as small, dispersed clusters.

At about the same time, a proto-Altaic language, the progenitor of the Turkic, Mongolian, and Manchu-Tungus languages, was spoken somewhere in the Central Eurasian Steppe; Proto-Berber and Proto-Semitic were spoken somewhere in the Middle East. In the Far East, the discovery of two pottery models of silkworm chrysalides and 70 shuttlelike objects at a 6th Millennium BCE site at Nanyangzhuang (southern Hebei) suggests the early production of silk, the characteristic Chinese textile.

In the Euphrates-Tigris delta, the earliest phase of prehistoric civilization developed, which has a parallel in Susiana, north of the Iranian frontier and, therefore, the first settlers in both areas may have a common origin. Among these settlers, according to some scholars, was the germ of Sumerian genius, but this is not indisputably authenticated until the end of the 4th millennium. By 3100 BCE, however, the presence of the Sumerians is finally proved by the invention of writing as a vehicle for their own language. From then onward, successive phases in the evolution of Sumerian art can satisfactorily be studied. By about 5000 BCE (16 seconds before the end of the Cosmic Calendar), large scale copper smelting has spread throughout the Middle East and North Africa.

By about 4500 BCE (15 seconds before the end of the Cosmic Calendar), the major part of the Danubian Expansion ended with the spread of the Stroke-Ornamented Ware Culture (German: Stichbandkeramik, abbr. STK or STbK), also known as the Ib level of Danubian Culture, or as the "Gordon Childe" or "Middle Danubian" culture. It is the successor of the Linear Pottery Culture, a major archaeological horizon of the European Neolithic in Central Europe. Centered on Silesia in Poland, Eastern Germany and the Northern Czech Republic, it overlaps with the Lengel Horizon to the South, and the Rössen Culture to the West. It is about this time that the Far East and Southeast Asian civilizations begin their chalcolithic period.

At about 4300 BCE, the oldest city-state of Ancient Sumer, Eridu, is established, introducing the Ubaid Cultural period to Southern Mesopotamia, which fully illustrates the sequence of the preliterate Ubaid civilization, with its long succession of superimposed temples portraying the growth and development of an elaborate mud-brick architecture. Although Sumer would be the foundation of the first great imperial civilization in Mesopotamia (due to the very high degree of social organization needed for the development of large-scale irrigation projects), the development of urban communities (although not imperial) had occurred earlier in the North, where large scale irrigation projects were not necessary but where the impetus for imperial development also did not exist.

By about 4000 BCE (14 seconds before the end of the Cosmic Calendar), the oldest culture known to be distinctly Egyptian, the Badarian Culture is widespread throughout the Nile Delta Region. This is a very simple, unsophisticated, chalcolithic culture with no discernible centralization in social structure. Gold smelting began about this time in Mesopotamia and North Africa. Weaving by use of a loom also began about this time in the same regions. At this time as well, a Proto-Indo-European language was first spoken in the Steppes of Central Asia near Southern Russia and Ukraine.

By about 3600 BCE (13 seconds before the end of the Cosmic Calendar), a more sophisticated Egyptian culture, the Amratian (Naqādah I) Culture, predominated in the region of the Upper Nile. There is evidence of political authority in the first painted symbol of a pharaonic crown. Social organization probably existed in the form of small to large city-states, each under their own pharoanic leadership in some areas. Also at this time, the aegian ancestors of the Phoenicians, a Semitic people, spread throughout and populated the regions of the Levant and North Africa, probably influencing the developing Egyptian culture. The culture of Minoan Crete, populated earlier by a people who spoke a language isolate known to archaeologists as Eteocypriot, was probably heavily influenced by the earlier-developing Egyptian and Phoenician cultures, and began to dominate the Greek peninsula and the area of the Aegean Sea until the rise of Mycenaean Culture in the Fifteenth Century BCE.

Also about this time, the earliest known wooden wheel used for transportation is found in Mesopotamia and also in the Caucasus. The tournette and, soon after, the fast potter's wheel also began to be used in Mesopotamia. The twenty-four hour day was used in Egypt and Sumeria. Cuneiform writing (wedge marks on clay tablets) first appeared in ancient Sumer and Hieroglyphic script in Egypt, which begins the period of literate, historic, human civilization. The very modern Uruk Culture (also known as the Erech–Jamdat Nasr period) replaces the Ubayd Culture in ancient Mesopotamia. The beginnings of monumental architecture in Mesopotamia are usually considered to have been contemporary with the founding of the first truly Sumerian cities and the invention of writing. Conscious attempts at architectural design during this so-called Protoliterate period (c. 3400–c. 2900 BCE) are recognizable in the construction of religious buildings.

There is, however, one temple, at Abū Shahrayn (ancient Eridu), that is a final rebuilding of a shrine the original foundation of which dates back to the beginning of the 4th millennium. The continuity of design has been thought by some to confirm the presence of the Sumerians throughout the temple’s history, dating Sumerian civilization to a date several hundred years earlier than previously thought. Typical temples of the Protoliterate period — both the platform type and the type built at ground level — are, however, much more elaborate both in planning and ornament than is found at Abū Shahrayn. Interior wall ornament at Abū Shahrayn often consisted of a patterned mosaic of terra-cotta cones sunk into the wall, their exposed ends dipped in bright colours or sheathed in bronze.

It has been thought that the rarity of stone in Mesopotamia contributed to the primary stylistic distinction between Sumerian and Egyptian sculpture. Practically all Sumerian sculpture served as adornment or ritual equipment for the temples and no clearly identifiable cult statues of gods or goddesses have yet been found. Relief carving in stone was a medium of expression popular with the Sumerians, rather than the fully-developed stone sculptures of the early Egyptians, and first appeared in a rather crude form in Sumeria in Protoliterate times. In a somewhat different category are the cylinder seals so widely utilized at this time. Prominent among their subjects is the complicated imagery of Sumerian mythology and religious ritual.

Also at this time, agricultural settlements began to spread more widely in the Indus valley, known to archaeologists as the Early Harrapan culture. The earliest of these provide clear links with the cultures along or beyond the western margins of the Indus valley. In the course of time, a remarkable change took place in the form of the Indus settlements, suggesting that some kind of closer interaction was developing, often over considerable distances, and that a process of convergence was under way. This continued for approximately 500 years and can now be identified as marking a transition toward the full urban society that emerged at Harappa and similar sites about 2600 BCE.

Within 200 years (about 3400 BCE), a very sophisticated Egyptian culture, the Gerzean (Naqādah II) Culture spread throughout the entire region of the Nile Valley and predominated until the unification of Upper and Lower Egypt by the Pharoah Menes in 2925 BCE. Toward the end of the period, pictographic writing on pottery, slate palettes, and stone appeared, under kings employing pharaonic iconography. Contact with western Asia during this time may have inspired the building of mud-brick niched architecture, the use of cylinder seals, and the adoption of certain ornamental motifs.

By about 3200 BCE (12 seconds before the end of the Cosmic Calendar), the mesopotamian cities of Ur, Kish, Lagash, Erech/Uruk, Sippar, Akshak, Larak, Nippur, Adab, Umma, Bad-tibira, and Larsa had become large, powerful, city-states in Sumer, where political power initially originated in the citizenry and a quasi-democratic form of power-sharing existed. As the rivalry between the cities for scarce resources increased, the democratic power of the citizenry was replaced by monarchy and several warring kingdoms, primarily Kish, Ur, Uruk, and Lagash. Dialects of Sumerian, a language isolate, was spoken in the various city-states.

Human Cultural Evolution During the Bronze Age (3000 - 1200 BCE)

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The first use of bronze in Mesopotamia around 3000 BCE (about 11.5 seconds before the end of the Cosmic Calendar) ushered in the second so-called Metal Age, the Bronze Age. Whereas the Chalcolithic Age coincided with the development of large-scale settlements and true civilization, the Bronze Age coincided with the emergence of the historic, so-called Great Civilizations. The large scale dyeing of fabric and the use of papyrus, wax candles, and high-tensile strength, braided rope occurred about this time. The colonization of the islands located in the Aegean Sea, between and including Crete and the Greek mainland, gave rise to the early Bronze Age Cycladic Culture.

About this time, the Sumerians developed complex systems of measurement and a place-value system for numeration. They developed algebraic methods for solving linear and quadratic equations. They also developed a method of calculating Pythagorean triples, indicating a knowledge of the principles underlying what would later be called the Pythagorean Theorem, as well developed the long method for calculating square roots. The Egyptians developed a much less sophisticated use of a system of multiplication and unit fractions. The Canaanites settled the area of the Levant about this time.

In 2925 BCE, Upper and Lower Egypt were united under Menes (also known as Narmer), the first pharaoh to rule over all of Egypt.[25] This was also the age of the Biblical legend of the Great Flood. In Mesopotamia, this period is known for the first royal inscription in that region - Mesilim, a "King of Kish." The title of King of Kish then rotated about the various city-states of Sumer, making it plausible that the seat of government for the entire polity depended on which city could exercise its dominance over the others. It is also at this time that pastoralist settlements appear throughout the Peninsular Indian Sub-Continent.

Around 2800 BCE (11 seconds before the end of the Cosmic Calendar), the legend of Etana, King of Kish, states that he is the first ruler to unite the different city-states of Ancient Sumer. Influenced by the Phoenicians, the Egyptians, and the developing Cycladic Culture of the Aegean, the Minoan Civilization of Crete, rose to dominate the area of the Eastern Mediterranean until it is itself dominated by Mycenae and the later developing Greek civilization about 1200 years later. The first Kingdom of Elam, the earliest kingdom in the Iranian plateau, is established and the Sumerians first used the abacus for the tabulation of sums and differences, allowing for a quick method of multiplication and division.

Around 2660 BCE (depending on the dating system used), the last King of Kish, Agga, is defeated by Gilgamesh, king of the First Dynasty of Uruk. On the Indian subcontinent, evidence of widespread trade in many commodities, an apparent uniformity of weights and measures, a common script, and a uniformity — almost a common currency — of the seals used, all indicated some measure of political and economic control and point to the great cities Mohenjo-Daro and Harappa as their centres. The presence of the great granaries on the citadel mounds in these cities and of the citadels themselves suggests — partly on the analogies of the cities of Mesopotamia — the existence of priest-kings, or at least a priestly oligarchy, that controlled the economy and civil government. The intellectual mechanism of this government and the striking degree of control implicit in it are still matters of speculation. Nor can scholars yet speak with any certainty regarding relations between the cities and surrounding villages. Much more research needs to be done, on many such topics, before the full character of the Indus civilization can be revealed.

On 2575 BCE, Snefru becomes Pharaoh of Egypt, ushering in the Fourth Dynasty of pharaonic rule and the beginning of the Old Kingdom, during which the Great Pyramid and associated pyramids at Ghiza, as well as the first monumental sculpture - the Great Sphinx - were built. About fifty years later (depending on the dating system used), the Elamites from Southwestern Iran conquer the Sumerian city-states. Around this time, glass-making began in Egypt from fine sands (silicon dioxide), for which potash (potassium carbonate mixed with various other potassium and sodium salts), distilled from the ashes of wood fires, is used to lower the melting point of the sand. The Sumerians created multiplication and division tables and applied this mathematics to geometric problems. Use of true fractions, simple algebra, quadratic and cubic equations, and the calculation of regular reciprocal pairs soon followed.

Also about this time, Semitic tribes migrated from the Arabian Peninsula, beginning c. 2500 BCE (10 seconds before the end of the Cosmic Calendar), to the Mediterranean coast (the Amorites), Mesopotamia (the Akkadians), and the Nile River delta. In Phoenicia, they became seafarers. In Mesopotamia, they blended with the civilization of Sumer. According to Biblical tradition, some of the Semites who settled in Ur later moved into Palestine and then, even later, into Egypt. The Hurrians (the Horites of the Old Testament) moved into Eastern Mesopotamia, probably from the Zagros Mountains in Western Iran. In the Far East, the elegant Longshan Culture predominated in China, characterized by fine burnished ware in wheel-turned vessels of angular outline, abundant gray pottery, rectangular polished stone axes, walls of compressed earth, and a method of divination by heating cattle bones and interpreting the cracks.

Around 2334 BCE, Sargon I of Akkad (reigned c. 2334 - 2279 BCE) conquered all of Southern Mesopotamia (Sumer) and a substantial part of the Middle East, establishing the Akkadian Empire. Although Sargon’s dynasty lasted only about 142 years, this dynasty united the city-states and created a model of government that influenced all of Middle Eastern civilization. The earliest known surviving map, dating probably from the time of Sargon of Akkad (about 2334 – 2279 BCE), shows canals or rivers—perhaps the Tigris and a tributary—and surrounding mountains. In addition at this time, soap-making industries existed in Mesopotamia. Soap is created by mixing potassium hydroxide, calcium hydroxide, or sodium hydroxide (collectively known as "alkali") with animal fat or vegetable oils. Potassium hydroxide, commonly known as "lye," was produced by boiling "potash" (wood ash) or "pearl ash" (potassium carbonate derived from wood ash that has been purified by baking it in a kiln). calcium hydroxide, also known as "slaked lime" was produced by dissolving "quicklime" (calcium oxide) in water. Quicklime was produced by baking limestone or chalk (both primarily composed of calcium carbonate) in lime kilns. Sodium carbonate, the other source of carbonate used for the production of lime, was also the embalming dessicant used by the Egyptians, "natron," which may be mined from dry lake beds in arid regions. As such, soap-making represents humanity's earliest chemical industry.

Around 2230 BCE, the semi-barbaric Gutians from the Zagros Mountains dominated the city-states of Akkad and Sumer for about 100 years. The end of Gutian domination coincides with the beginning of the First Intermediate Period in Egypt at 2130 BCE. About this time, Akkadian, a Semitic language, has become the lingua franca of Mesopotamia, replacing the Sumerian language in Southern Mesopotamia, a legacy of the Akkadian conquest of Sargon I.

Around 2117 BCE, The amorites conquered and governed Akkad and Sumer, as well as invaded Canaan. Amorite rule persisted until 1763 BCE (depending on the dating system used), when Hamurrabi of Babylon conquers all of Mesopotamia, establishing the Old Empire of Babylon and promulgating his famous code of laws for the entire empire. Unlike the absolutist pharaonic system, the Code of Hamurrabi establishes the world's first imperial legal system. However, Hamurrabi's code was not the first. King Ur-Nammu (reigned c. 2112 - 2095 BCE) of the Third Dynasty of Ur published the earliest law code known in Mesopotamia (9 seconds before the end of the Cosmic Calendar). The Old Babylonian Empire existed until about 1450 BCE when they were conquered by Kassite and Mitanni from the Zagros Mountains and what would later become Persia and Western Iran.

Elsewhere, the Chinese and Southeast Asian civilizations began their bronze age. A proto-Sino-Tibetan language was also spoken somewhere in the Far East and the spoked wheel was invented. Soon afterward, the earliest, fully-developed chariots appeared in the Andronovo Culture of Southern Russia and Kazakhstan in the Steppes of Central Asia, and thereafter spread to the Middle East, ostensibly at the hands of invading forces. The ancient Phoenician city of Tyre had become an important trading city and port in the Levant of the Eastern Mediterranean, and the earliest references to simple, glass, meniscal lenses existed in Egyptian hieroglyphics.

Around this time, Proto-Indo-Iranian, an Indo-European language, was spoken in the West Asiatic Steppes and in Western Siberia. Coincident with this development was the commencement of the decline of the urban Indus civilization, which also coincided with the arrival of Indo-Iranian speaking groups. This probably occurred in several stages and perhaps over a century or more, possibly in a manner similar to the migration of Doric peoples into mainland Greece a thousand years later. The collapse of the urban system did not necessarily imply a complete breakdown in the lifestyle of the population in all parts of the Indus region, but it seems to have involved the end of whatever system of social and political control had preceded it. After that date the cities, as such, and many of their distinctively urban traits — the use of writing and of seals and a number of the specialized urban crafts — disappeared. The succeeding era, which lasted until about 750 BCE, may be considered as Post-Harappan or, perhaps better, as “Post-Urban.”

In 1938 BCE, Mentuhotep II inaugurated the Eleventh Dynasty and the commencement of the Middle Kingdom in Egypt. Within 100 years, the first known use of a true arch was built into the gate to the community of Ashqelon in the Levant. Anatolian, the oldest known, fully evolved, Indo-European language, was spoken about this time. Kassite and, later, Mitanni settlements had emerged in the area of what would later become Western Iran. About this time, iron smelting began. Use of coal in bloomeries to produce steel appeared several hundred years later (by at least 1300 to 1200 BCE, depending on the region). However, the large-scale use of iron and steel, primarily as weapons, would not occur at the earliest until about 1200 BCE in the Middle East and Southeastern Europe, and not until around 600 BCE in the Far East.

In 1630 BCE, an asiatic people, called the Hyksos, invaded and conquered Egypt from the north via Canaan. The Hyksos introduced the horse and chariot, the compound bow, improved battle axes, and advanced fortification techniques into the Middle East and Egypt. The Hyksos invasion commenced the Second Intermediate Period in Egypt. During this time, Indo-Hittite, an Indo-European language, was spoken in Anatolia and Proto-Greek and Paleo-Balkan, also Indo-European languages, were spoken in the region of the Balkans. Mycenaean civilization existed on the Greek mainland.

Also during this time, The Shang dynasty — the first Chinese dynasty to leave historical records — is thought to have ruled from about 1600 to 1046 BCE (Some scholars date the Shang from the mid-18th to the late 12th century BCE). One must, however, distinguish Shang as an archaeological term from Shang as a dynastic one. Erlitou, in north-central Henan, for example, was initially classified archaeologically as Early Shang; its developmental sequence, from about 2400 to 1450 BCE, documents the vessel types and burial customs that link Early Shang culture to the Late Neolithic cultures of the East. In dynastic terms, however, Erlitou Periods I and II (c. 1900 BCE?) are now thought by many to represent a pre-Shang (and thus, perhaps, Xia) horizon. In this view, the two palace foundations, the elite burials, the ceremonial jade blades and sceptres, the bronze axes and dagger axes, and the simple ritual bronzes — said to be the earliest yet found in China — of Erlitou III (c. 1700–1600 BCE?) signal the advent of the dynastic Shang. The ritual schedule records 29 royal ancestors over a span of 17 generations who, from at least Wuding to Dixin, were each known as wang (“king”). Presiding over a stable politico-religious hierarchy of ritual specialists, officers, artisans, retainers, and servile peasants, these rulers governed with varying degrees of intensity over the North China Plain and parts of Shandong, Shanxi, and Shaanxi, mobilizing armies of at least several thousand men as the occasion arose.

Around 1560 BCE, invasians by the Kassites and Mitanni, migrating from the Zagros Mountains in what would later be called Western Iran, ushered in a "dark ages" in most of Mesopotamia. The Mitanni Kingdom eventually asserted sole control of this region of Mesopotamia and the territory east of the Zagros mountains occupied by them and the Kassites by about 1500 BCE and maintained control until finally defeated by the Assyrians in 1234 BCE.

In 1539 BCE (8 seconds before the end of the Cosmic Calendar), Pharaoh Ahmose ejected the Hyksos from Egypt and thereby commenced the 18th Dynasty of Egypt and the beginning of the New Kingdom, which would exist until Egypt was conquered by the Persians in 525 BCE.

Around this time, the oldest Indo-Aryan language, Old-Indo-Vedic, a sub-group of the Indo-Iranian language group, was spoken in the area of the Ganges River. Composed in archaic, or Vedic, Sanskrit, and generally dated between 1500 and 800 BCE, and transmitted orally, the Vedas comprised four major texts — the Rig-, Sama-, and Yajur-Vedas, and the Atharvaveda. Of these, the Rigveda is believed to be the earliest. The texts consisted of hymns, charms, spells, and ritual observations current among the Indo-European-speaking people of the time, known to themselves as "Aryans" (from Sanskrit arya, “noble”), who presumably entered India from the eastern regions of the Iranean Plateau.

The early Vedic was the period of transition from nomadic pastoralism to settled village communities intermixing pastoral and agrarian economies. Cattle were initially the dominant commodity, as indicated by the use of the words gotra (“cowpen”) to signify the endogamous kinship group and gavishti (“searching for cows”) to denote war. A patriarchal, extended family structure gave rise to the practice of niyoga (levirate), which permitted a widow to marry her husband’s brother. A community of families constituted a grama. The term vish is generally interpreted to mean “clan.” Clan assemblies appear to have been frequent in the early stages. Various categories of assemblies are mentioned, such as vidatha, samiti, and sabha, although the precise distinctions between these categories are not clear. The clan also gathered for the yajna, the Vedic sacrifice conducted by the priest, whose ritual actions ensured prosperity and imbued the chief with valour. The chief was primarily a war leader with responsibility for protecting the clan, for which function he received a bali (“tribute”). Punishment was exacted according to a principle resembling the wergild of ancient Germanic law, whereby the social rank of a wronged or slain man determined the compensation due him or his survivors.

In 1479 BCE, Thutmose III, considered by many to be the greatest of all Egyptian pharaohs, expanded Egyptian domination over the entire Levant and into Southern Mesopotamia, creating what has been called the "Egyptian Empire." The Egyptian Empire would persist until approximately 1185 BCE when, during the reign of Ramses III, the Levant and Nile Delta were invaded by the "sea peoples," peoples of Aegean origin who settled on the southern coast of the Levant in the 12th century BCE and possibly of Doric Greek origin, about the same time as the arrival of the Israelites after their exodus from Egypt.

Around 1450 BCE, the Kassites, and ultimately the Mitanni, conquered and governed the Babylonian Empire. Mitanni dominance of most of Mesopotamia and the region of the Zagros Mountains and western Iranian Plateau would persist until 1295 BCE when they were conquered by the Assyrians under Adad-Nirari I.

At about the same time as the Kassite and Mitanni invasion of Mesopotamia, Crete suffered a major earthquake that destroyed Knossós and other population centres on that island, with power in the region then passing decisively to the Mycenaeans of what would later be called northern Greece, and with whom Crete was closely associated until the commencement of the Iron Age around 1200 BCE. Subsequent to 1200 BCE, the Dorians, another Greek-speaking people, moved in and organized the island.

In 1380 BCE, Suppiluliumas I established the Hittite Empire which vied with Egypt for control of the Levant and Mesopotamia. The greatest extent of the Hittite Empire was reached at the Battle of Kadesh, where the Hittites and the Egyptians battled to a standoff. Both the Hittite and Egyptian Empires collapsed around 1185 due to the invasions of the so-called "sea peoples." The people of Troy mentioned in Homer's Iliad were most likely Hittites.

In 1340 BCE, Ashur-Uballi I freed the Akkadian city-state of Ashur from Mitanni control and began the expansion of what would later come to be called the Assyrian Empire. In 1295 BCE, the Mitanni are finally defeated by the Assyrians under Adad-Nirari I. The Assyrians later lose large parts of their empire to the Hittites in 1264 BCE.

Human Cultural Evolution During the Iron Age (1200 BCE to the Present)

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In terms of cultural development, human beings have continued to exist in the Iron Age to the present day. Therefore, the Iron Age can be divided into the following periods of cultural development: the Early Iron Age Civilizations, lasting from about 1200 BCE to about 500 BCE; the Age of the Ancient Imperial Civilizations of the Later Iron Age, lasting from about 500 BCE to about 500 CE; the Age of the Medieval Civilizations, lasting from about 500 CE to about 1400 CE; and Modern Civilization, lasting from about 1400 CE to the present day. The Period of Modern Civilization for human cultural development can also be further subdivided into the periods of the Rennaissance and Enlightenment (c. 1400 to c. 1750); Industrial Revolution (c. 1750 to c. 1950); and the Information Age (c. 1950 to the present day).

Early Iron Age Civilizations (1200 - 500 BCE)

By 1200 BCE (about 7.3 seconds before the end of the Cosmic Calendar), the large-scale use of iron and steel, primarily as weapons, occurs in the Middle East and Southeastern Europe. In the Far East, Proto-Chinese (the mother language from which all Chinese dialects descend) is spoken and the spoked wheel chariot makes its first appearance. This is also approximately the time of the Hebrew Exodus from Egypt during the reign of Pharaoh Ramses II.

Doric culture, a major division of the ancient Greek people, began its spread throughout the Aegean and Eastern Mediteranean at about this time and is distinguished by a well-marked dialect, as well as by their subdivision into the “tribes” (phylai) of Hylleis, Pamphyloi, and Dymanes - tribal divisions that existed within all their communities. These three tribes were apparently quite separate in origin from the four tribes found among the Ionian Greeks that also populated the Aegean at this time. The Doric peoples are traditionally acknowledged as the conquerors of the Peloponnese during the Twelfth Century, ushering in the "Dark Ages" of Archaic Greece. If it actually happened, the Trojan War depicted in Homer's Iliad and Odyssey probably occurs about this time on the West Coast of Anatolia.

Also about this time, an "invasion" of "sea peoples" occurred throughout the Levant and the Nile River Delta. These so-called Sea Peoples were of Aegean origin and settled on the Southern coast of Palestine in the 12th century BCE, about the time of the arrival of the Israelites after their exodus from Egypt, and were possibly of Doric origin. According to biblical tradition (Deuteronomy 2:23; Jeremiah 47:4), the Philistines came from "Caphtor" (possibly Crete). They are mentioned in Egyptian records as "prst," one of the Sea Peoples that invaded Egypt in about 1190 BCE, after ravaging Anatolia, Cyprus, and Syria. After being repulsed by the Egyptians, they occupied the coastal plain of Palestine from Joppa (modern Tel Aviv–Yafo) southward to the Gaza Strip. This area contained the five cities (the Pentapolis) of the Philistine confederacy (Gaza, Ashkelon, Ashdod, Gath, and Ekron) and was known as Philistia, or the Land of the Philistines. It was from this designation that the whole of the country was later called Palestine by the Greeks. Other Sea Peoples of this period who invaded the Levant and Egypt, but who did not remain in the areas they invaded, are the Achaeans (which may have included the Dorians, see below), Etruscans, Luka, Sardinians who called themselves the Sherden (and who acted as mercenaries for the Egyptians), and the Shekelesh from Sicily. Around 1185 BCE, the Egyptian and Hittite Empires collapsed under pressure from the invasions of these Sea Peoples.

Around 1152 BCE, Marduk-kabit-ahheshu established the Second Dynasty of Isin, during which the Kassites were completely Babylonianized, firmly establishing the Assyrian Empire in Mesopotamia. Around 1100 BCE, a proto-Villanovan Culture was present in Northern Italy, later giving rise to the Villanovan Culture proper about 900 BCE and then, later, to the Estruscan Civilization. Also around 1100, Aeolian-speaking Greeks colonized the West coast of Anatolia. The New Kingdom of Egypt ended with the death of Pharaoh Ramses XI in 1075 BCE, from which followed a period of political instability and Assyrian domination that lasted until a short period of renewed stability began about 664 BCE with the establishment of the XXVI Dynasty of Pharaoh Psamtik I and the beginning of what has been called the Late Period of Ancient Egypt.

From about 1046 BCE, and until about 256 BCE, the Zhou Dynasty is the predominant political power in East Asia. The vast time sweep of the Zhou dynasty — encompassing some eight centuries—is the single longest period of Chinese history. However, the great longevity of the Ji lineage was not matched by a similar continuity of its rule. During the Xi (Western) Zhou (1046–771 BCE), the first of the two major divisions of the period, the Zhou court maintained a tenuous control over the country through a network of feudal states. This system broke down during the Dong (Eastern) Zhou (770–256 BCE), however, as those states and new ones that arose vied for power. The Dong Zhou is commonly subdivided into the Chunqiu (Spring and Autumn) period (770–476 BCE) and the Zhanguo (Warring States) period (475–221 BCE), the latter extending some three decades beyond the death of the last Zhou ruler until the rise of the Qin Dynasty in 221.

Around 1021 BCE, Saul becomes the first King of Ancient Israel. Around 1,000 BCE (7 seconds before the end of the Cosmic Calendar), David succeeds Saul as King of Ancient Israel and unites the entire country at his capital at Jerusalem. At this time, the earliest, fully-developed alphabetic system of writing, the North-Semitic Alphabet, is developed somewhere in Anatolia. The Old Hebrew script differs very little from the North Semitic script. Biblical Aramaic Culture and the more modern form of Phoenician Culture also developed in this area at this time. Around 962 BCE, Solomon succeeds David as King of Israel at the height of its regional power and builds the first Temple of Solomon in Jerusalem.

Around 900 BCE, the Moabites settled in what is now West-Central Jordan, just east of the Dead Sea. Also about this time, the Greek Ionians are said to have migrated to western Anatolia from Attica and other central Greek territories, following from the Doric migrations that upset the Achaean kingdoms on the mainland. This is confirmed by the fact that the same four “tribes” (phylai) found among the Athenians reappear in the inhabitants of Miletus and other Ionian cities. The early Greeks adopted and modified the Phoenician alphabet (probably itself descending from the North Semitic alphabet) for use by the Greek language. The Latin alphabet ultimately descended from the Greek alphabet via the Etruscan alphabet.

Around 850 BCE, the Medes established the first truly Persian culture on the Iranian Plateau. 814 BCE is the traditional date for the founding of the ancient city of Carthage by the Phoenicians of Tyre. Around 800 BCE is the earliest known settlement of the Palatine Hill known to archaeology in what would later become the city of Rome, which corresponds roughly with the traditional date for the founding of that city in 753 BCE. Also around 800 BCE, the Dark Ages of Archaic Greece came to a conclusion and the supposed poet Homer composed the epic stories of the Iliad and the Odyssey. Also about this time, Proto-Italo-Celtic, an Indo-European language, was probably spoken in Western Europe. Gold and silver coins were also generally used as currency. The first Olympic Games were held in Messene, Greece, 776 BCE.

Elsewhere, in the South Asian subcontinent, beginning around 800 BCE and lasting until about 500 BCE, Late Vedic Culture flourishes. The principal literary sources from this period are the Brahmanas (manuals on ritual) and the Upanishads (Upanisads) and Aranyakas (collections of philosophical and metaphysical discourses). Associated with the corpus are the sutra texts, largely explanatory aids to the other works, comprising manuals on sacrifices and ceremonies, domestic observances, and social and legal relations. Because the texts were continually revised, they cannot be dated accurately to the early period. The Dharma-sutra texts of this period became the nuclei of the socio-legal Dharma-shastras of later centuries. The geographic focus of the later Vedic corpus moves from the Sapta Sindhu region into the Ganges–Yamuna Doab and the territories on its fringe. The areas within this land of the aryas, called Aryavarta, were named for the ruling clans, and the area encompassed within Aryavarta gradually expanded eastward. By the end of the period, clan identity had changed gradually to territorial identity, and the areas of settlement came eventually to form states. The people beyond the Aryavarta were termed the mlecchas (or mlechchhas), the "impure barbarians" unfamiliar with the speech and customs of the aryas. Siddhārtha Gautama, also known as the Buddha, is born sometime at the very end of this period and founds the religion of Buddhism, which is a philosophical outgrowth of Late Vedic thought.

Around 750 BCE, mineral crystals were used as light-focusing lenses by the Assyrians. In 746 BCE, after a period of turmoil, rebellion, and plague, Tiglath-pileser III consolidated and expanded the "Neo-Assyrian Empire" to its greatest territorial extent. In 728 BCE, Deioces established the first Kingdom of the Medes, Media, in Persia. Median dynastic power governs Persia until Achaemenian rule is established in 529 BCE. Around 700 BCE, the Etruscans had become the dominant power in Northern Italy and Ionian Greek settlers had established colonies in Sicily and on the coast of the Southern Italian peninsula.

Around 700 BCE, Archilochus of Paros writes the first known lyric poetry. Also around 700 BCE, Hesiod of Boeotia wrote two works: Works and Days, and Theogony. The first is a faithful depiction of the poverty-stricken country life he knew so well and sets forth principles and rules for farmers. Theogony is a systematic account of creation and of the gods. It vividly describes the ages of mankind, beginning with a long-past Golden Age. Together the works of Homer and Hesiod comprised a kind of Bible for the Greeks; Homer told the story of a heroic, relatively near past, which Hesiod bracketed with a creation narrative and an account of the practical realities of contemporary daily life.

About this time, the religion of Jainism was established in the India subcontinent. Jainism teaches a path to spiritual purity and enlightenment through a disciplined mode of life founded upon the tradition of ahimsa, nonviolence to all living creatures. Beginning in the 7th–5th century BCE, Jainism evolved into a cultural system that has made significant contributions to Indian philosophy and logic, art and architecture, mathematics, astronomy and astrology, and literature. Along with Hinduism and Buddhism, it is one of the three most ancient Indian religious traditions still in existence. The name Jainism derives from the Sanskrit verb ji, “to conquer.” It refers to the ascetic battle that, it is believed, Jain renunciants (monks and nuns) must fight against the passions and bodily senses to gain omniscience and purity of soul or enlightenment. The most illustrious of those few individuals who have achieved enlightenment are called Jina (literally, “Conqueror”), and the tradition’s monastic and lay adherents are called Jain (“Follower of the Conquerors”), or Jaina. This term came to replace a more ancient designation, Nirgrantha (“Bondless”), originally applied to renunciants only.

From about 670 to 660 BCE, Roman settlements have extended to the Esquiline and then the Quirinal Hills and finally down into what became the Roman Forum, thus establishing Rome as a Latin urban center. Beginning in 664 BCE, the XXVI Dynasty of the so-called "Late Dynastic Period" begins in Egypt, which period lasts until Egypt is conquered by the Persians under Cambyses II in 525. Around 650 BCE, "tyrannical" individuals began rising up and seizing control of the government of Greek city-states in opposition to what was regarded as oppression by the local, ruling aristocracy. The so-called "Age of the Tyrants" was considered by the Greeks to have ended when Hippias, son of Peisistratus, who had previously established a tyranny at Athens in the middle of the 6th century, was expelled by King Cleomenes I of Sparta in 510 BCE.

Around 630 BCE (6 seconds before the end of the Cosmic Calendar), an Athenian statesman known as one of the Seven Wise Men of Greece, Solon ended exclusive aristocratic control of the government, substituting a system of control by the wealthy, and introducing a new and more humane law code. He was also a noted poet. Also around 630 BCE, Nabopolassar became king of the Chaldeans and, in c. 626 BCE, ejected the Assyrians from Uruk and declared himself king of Babylonia. During his reign until his death in 605 BCE, Nabopolassar extended his control throughout the Assyrian Empire and his son, Nebuchadrezzar II (reigned 605-561), was responsible for the Babylonian Captivity of Israel (c. 587-528 BCE). Around 625 BCE, Cyaxares established the Median Kingdom in Northwest Iran until it was overthrown by Cyrus II in 550 BCE. By 600 BCE, the large-scale use of iron and steel, primarily as weapons, occurred in the Far East.

From about 624 until 548/545 BCE, Thales of Miletus lived and is considered by many to be the first Greek philosopher. In Thales’ time the word philosopher (“lover of wisdom”) had not yet been coined. Thales was counted, however, among the legendary Seven Wise Men (Sophoi), whose name derived from a term that then designated inventiveness and practical wisdom rather than speculative insight. Thales demonstrated these qualities by trying to give the mathematical knowledge that he derived from the Babylonians a more exact foundation and by using it for the solution of practical problems — such as determining the distance of a ship as seen from the shore or the height of the Egyptian pyramids. Although he was also credited with predicting an eclipse of the Sun, it is likely that he merely gave a natural explanation of one on the basis of Babylonian astronomical knowledge. He held that everything had come out of water — an explanation based on the discovery of the fossilized remains of sea animals found far inland. As such, Thales is the first person known to history to ascribe wholly natural explanations for natural phenomena rather than explanations grounded in mythology. Thales was also the first to write about static electricity and how it could be produced by rubbing certain substances together, which was the very first, known scientific description of a natural phenomenon - i.e., static electricty.

From about 610 until 546 BCE, Anaximander of Miletus (a student of Thales) lived and attempted to give a more elaborate account of the origin and development of the ordered world (the cosmos) than his mentor. According to Anaximander, the cosmos developed out of the apeiron (“unlimited”), something both infinite and indefinite (without distinguishable qualities). Within this apeiron something arose to produce the opposites of hot and cold. These at once began to struggle with each other and produced the cosmos. The cold (and wet) partly dried up (becoming solid earth), partly remained (as water), and—by means of the hot—partly evaporated (becoming air and mist), its evaporating part (by expansion) splitting up the hot into fiery rings, which surround the whole cosmos. Because these rings are enveloped by mist, however, there remain only certain breathing holes that are visible to human beings, appearing to them as the Sun, Moon, and stars. Anaximander was the first to realize that upward and downward are not absolute but that downward means toward the middle of the Earth and upward away from it, so that the Earth had no need to be supported (as Thales had believed) by anything. Starting from Thales’ observations, Anaximander tried to reconstruct the development of life in more detail. Life, being closely bound up with moisture, originated in the sea. All land animals, he held, are descendants of sea animals; because the first humans as newborn infants could not have survived without parents, Anaximander believed that they were born within an animal of another kind—specifically, a sea animal in which they were nurtured until they could fend for themselves. Gradually, however, the moisture will be partly evaporated until, in the end all things will return into the undifferentiated apeiron, “in order to pay the penalty for their injustice”—that of having struggled against one another.

Also born about 610 BCE and living until about 570 BCE, Sappho (also spelled Psappho in the Aeolic dialect spoken by the poet) of Lesbos (now part of Greece) was a Greek lyric poet greatly admired in all ages for the beauty of her writing style. She ranks with Archilochus (living around 650 BCE) and Alcaeus (c. 620 - c. 580 BCE), among Greek poets, for her ability to impress readers with a lively sense of her personality. Her language contains elements from Aeolic vernacular speech and Aeolic poetic tradition, with traces of epic vocabulary familiar to readers of Homer. Her phrasing is concise, direct, and picturesque. She has the ability to stand aloof and judge critically her own ecstasies and grief, and her emotions lose nothing of their force by being recollected in tranquillity.

From about 570 until 500/490 BCE, Pythagoras of Samos, founded a fraternal philosophical school governed by strict rules. He appears to have brought his doctrine of the transmigration of souls from the Middle East. Much more important for the history of philosophy and science, however, was his doctrine that “all things are numbers,” which means that the essence and structure of all things can be determined by finding the numerical relations they express. Originally, this, too, was a very broad generalization made on the basis of comparatively few observations: for instance, that the same harmonies can be produced with different instruments — strings, pipes, disks, etc. — by means of the same numerical ratios — 1:2, 2:3, 3:4 — in one-dimensional extensions; the observation that certain regularities exist in the movements of the celestial bodies; and the discovery that the form of a triangle is determined by the ratio of the lengths of its sides. This was the first logical proof of the truth of what has become known as the "Pythagorean Theorem" (also known as the "47th Problem of Euclid"), a mathematical relationship that had already been in use for thousands of years by the Babylonians, Indians and Egyptians.

In 559 BCE, Cyrus II of Persia conquered the Medians of Iran and extended the Persian Empire from the Mediterranean Sea to the Indus River, thereby absorbing the remnants of the Egyptian Empire, but he did not attempt to conquer Egypt itself. Around 550 BCE, Cosmas, an Alexandrian geographer writing in the 6th century, knew that Tzinitza (China) could be reached by sailing eastward, but he added: "One who comes by the overland route from Tzinitza to Persia makes a very short cut," thus providing important geographical information to other ancient and, particularly, later medieval Western explorers exploring overland trade routes between the West and China. Also about this time, Armenian culture predominated in the region of the Trans-Caucasus and the relatively unrelated Aramaic language had become the lingua franca of the Middle East.

In 551 BCE, China’s most famous teacher, philosopher, and political theorist, whose ideas have influenced the civilization of East Asia, Confucious is born. Confucius’s life, in contrast to his tremendous importance, seems starkly undramatic, or, as a Chinese expression has it, it seems “plain and real.” The plainness and reality of Confucius’s life, however, underlines that his humanity was not revealed truth but an expression of self-cultivation, of the ability of human effort to shape its own destiny. The faith in the possibility of ordinary human beings to become awe-inspiring sages and worthies is deeply rooted in the Confucian heritage, and the insistence that human beings are teachable, improvable, and perfectible through personal and communal endeavour is typically Confucian.

Around 545 BCE, Anaximenes of Miletus (a student of Thale's Milesian School), taught that air was the origin of all things. His position was for a long time thought to have been a step backward because, like Thales, he placed a special kind of matter at the beginning of the development of the world. But this criticism missed the point. Neither Thales nor Anaximander appear to have specified the way in which the other things arose out of water or apeiron. Anaximenes, however, declared that the other types of matter arose out of air by condensation and rarefaction. In this way, what to Thales had been merely a beginning became a fundamental principle that remained essentially the same through all of its transmutations. Thus, the term arche, which originally simply meant “beginning,” acquired the new meaning of “principle,” a term that henceforth played an enormous role in philosophy down to the present. This concept of a principle that remains the same through many transmutations is, furthermore, the presupposition of the idea that nothing can come out of nothing and that all of the comings to be and passings away that human beings observe are nothing but transmutations of something that essentially remains the same eternally. In this way it also lies at the bottom of all of the conservation laws—the laws of the conservation of matter, force, and energy—that have been basic in the development of physics. Although Anaximenes of course did not realize all of the implications of his idea, its importance can hardly be exaggerated.

From about 560 until 478 BCE, Xenophanes of Colophon (also of the Milesian School) was the first to articulate more clearly what was implied in Anaximenes’ philosophy. He criticized the popular notions of the gods, saying that people made the gods in their own image. But, more importantly, he argued that there could be only one God, the ruler of the universe, who must be eternal. For, being the strongest of all beings, he could not have come out of something less strong, nor could he be overcome or superseded by something else, because nothing could arise that is stronger than the strongest. The argument clearly rested on the axioms that nothing can come out of nothing and that nothing that exists can vanish.

From about 540 until 480 BCE, Heracleitus of Ephesus (founder of the Ephesian School of philosophy) lived and stressed the need for people to live together in social harmony, though he was primarily concerned with explanations of the natural world from which this view arose. He complained that most people failed to comprehend the logos (Greek: “reason”), the universal principle through which all things are interrelated and all natural events occur, and thus lived like dreamers with a false view of the world. A significant manifestation of the logos, Heracleitus claimed, is the underlying connection between opposites. For example, health and disease define each other. Good and evil, hot and cold, and other opposites are similarly related. As such, Heracleitus concept of the "logos" informed all later philosophy with the importance of reason and became a fundamental principle upon which later Christian theology would be grounded.

In addition, Heracleitus noted that a single substance may be perceived in varied ways — e.g., seawater is both harmful (for human beings) and beneficial (for fishes). His understanding of the relation of opposites to each other enabled him to overcome the chaotic and divergent nature of the world, and he asserted that the world exists as a coherent system in which a change in one direction is ultimately balanced by a corresponding change in another. Between all things there is a hidden connection, so that those that are apparently “tending apart” are actually “being brought together.” Viewing fire as the essential material uniting all things, Heracleitus wrote that the world order is an “ever-living fire kindling in measures and being extinguished in measures.” He extended the manifestations of fire to include not only fuel, flame, and smoke but also the ether in the upper atmosphere. Part of this air, or pure fire, “turns to” ocean, presumably as rain, and part of the ocean turns to earth. Simultaneously, equal masses of earth and sea everywhere are returning to the respective aspects of sea and fire. The resulting dynamic equilibrium maintains an orderly balance in the world. This persistence of unity despite change was illustrated by Heracleitus’ famous analogy of life to a river: “Upon those who step into the same rivers different and ever different waters flow down.” Plato later took this doctrine to mean that all things are in constant flux, regardless of how they appear to the senses. Heracleitus was unpopular in his time and was frequently scorned by later biographers. His primary contribution lies in his apprehension of the formal unity of the world of experience.

From 529 until 330 BCE, Kings of the Achaemanian Dynasty governed Persia until Persia's final conquest by Alexander the Great in 330 BCE. In 525 BCE, Egypt was conquered by the Persian King Cambyses II and remained under Persian domination as the puppet XXVII Dynasty (First Achaemenid Period) of the so-called "Late Dynastic Period" until the death of the Persian King Darius II in 404 BCE.

Aeschylus, living from 525/524 BCE until 456/455 BCE, was the first of classical Athens’ great dramatists, who raised the emerging art of tragedy to great heights of poetry and theatrical power. He is most famous for his Oresteia. The only surviving example of a trilogy of ancient Greek plays, the Oresteia was originally performed at the Dionysia festival in Athens in 458 BC, where it won first prize. A principal theme of the trilogy is the shift from the practice of personal vendetta to a system of litigation. The name derives from the character Orestes, who sets out to avenge his father's murder.

In 515 BCE, the Second Temple of Solomon was established in Jerusalem, effectively signaling the end of the Babylonian captivity of the Jewish people. However, Palestine remained under effective Persian control until that control changed hands to the Ptolemies after the conquest of Alexander the Great in the late Fourth Century BCE.

Born about 515 BCE, Parmenides of Elea founded the so-called school of Eleaticism, of whom Xenophanes has been regarded as his primary teacher and forerunner. In a philosophical poem, Parmenides insisted that “what is” cannot have come into being and cannot pass away because it would have to have come out of nothing or to become nothing, whereas nothing by its very nature does not exist. There can be no motion either, for it would have to be a motion into something that is—which is not possible since it would be blocked—or a motion into something that is not—which is equally impossible since what is not does not exist. Hence, everything is solid, immobile being. The familiar world, in which things move around, come into being, and pass away, is a world of mere belief (doxa). In a second part of the poem, however, Parmenides tried to give an analytical account of this world of belief, showing that it rested on constant distinctions between what is believed to be positive—i.e., to have real being, such as light and warmth—and what is believed to be negative—i.e., the absence of positive being, such as darkness and cold.

In 510 BCE, the Greek "Age of the Tyrants" ended when Hippias, son of Peisistratus, who had previously established a tyranny at Athens in the middle of the 6th century, was expelled by King Cleomenes I of Sparta. During the next year (509), the last of the Etruscan kings was expelled from Rome when the aristocracy of Rome ejected the last of the Etruscan Kings from their city and replaced his rule with the joint authority of the Senate (an assembly of nobles appointed by the patrician aristrocrats but originally appointed by the pre-republic kings), two Consuls (elected by the Comitia Centuriata), and a popular assembly of the Roman tribes called the Comitia Tribuna - a system of government that would persist until the First Century BCE. At this time, Rome also negotiated her first treaty with the powerful Phoenician city-state in North Africa, Carthage. In 508 BCE, Cleisthenes established a democratic form of government for the city state of ancient Athens.

Soon after the collapse of the Etruscan Empire, the Latin League, a confederation of Latin cities located on the plane of Latium, organized due to the fact that the plain of Latium was threatened by the surrounding hill tribes - Sabines, Aequi, and Volsci (who experienced overpopulation and constantly tried to acquire more land) - as a consequence of the regional power vacuum left by the collapse. In 499/496, Rome fought the Latin cities at the Battle of Lake Regillus and the consul Spurius Cassius Vecellinus made a treaty with the Latins on an equal basis for mutual defense (493). As Rome gained territory, the political power of the league diminished. The treaty was renewed in 358 with changes that secured Rome’s leadership. This led to an outbreak of war from which Rome emerged victorious in 338, when the Latin League was dissolved.

Ancient Imperial Civilizations of the Later Iron Age (500 BCE - 500 CE)

500 BCE - 1 BCE

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From around 500 BCE, stories survive of a few men who are credited with bringing new knowledge from distant journeys. Herodotus tells of five young adventurers of the tribe of the Nasamones living on the desert edge of Cyrenaica in North Africa, who journeyed southwest for many months across the desert, reaching a great river flowing from west to east; this presumably was the Niger, although Herodotus thought it to be the Upper Nile. Also around this time, Hanno the Carthiginian explored the West Coast of Moroccon Africa and established several colonies. Himilco, another Carthaginian, also sailed north from Gibraltar and explored the Coast of Spain and France as far North as Brittany. Proto-Germanic, an Indo-European language and an ancestor of the Nordic languages, was spoken in Western Europe at this time and Hippasus of Metapontum, of the Pythagorean School, made one of the most fundamental discoveries in the entire history of science: that the side and diagonal of simple figures such as the square and the regular pentagon are incommensurable (i.e., their quantitative relation cannot be expressed as a ratio of integers), thereby discovering the existence of what later came to be called the "irrational" numbers. At first sight, Hippasus' discovery seemed to destroy the very basis of the Pythagorean philosophy and the school thus split into two sects: one group engaged in rather abstruse numerical speculations, while the other succeeded in overcoming the difficulty by ingenious mathematical inventions. Pythagorean philosophy also exerted a great influence on the later development of Plato’s thought.

By the end of the 6th century, Sparta had become the most powerful state in the Peloponnese, and was the political and military hegemon over Argos, the next most powerful state. Sparta acquired two powerful allies, Corinth and Elis, by ridding Corinth of tyranny and helping Elis secure control of the Olympic Games. Sparta also defeated Tegea in a frontier war and offered them a permanent defensive alliance; however, this was the turning point for Spartan foreign policy. Many other states in the central and provincial northern Peloponnese joined what has been called the Peloponnesian League, which eventually included all the Peloponnesian states except Argos and Achaea.

From 499 to 494 BCE, the Ionion cities of Anatolia deposed their Persian-imposed rulers and were then crushed by the Persian armies of Darius I. In 490 BCE, a subsequent Persian invasion of Greece was then repulsed in one of the greatest battles in military history at the Battle of Marathon. Using the Ionion Revolt as a pretext, Darius I landed a Persian army of 25,000 men unopposed on the Plain of Marathon and the Athenians appealed to Sparta to join forces against the invader. Owing to a religious festival, the Spartans were detained and 10,000 Athenians had to face the Persians aided only by 1,000 men from Plataea. The Athenians were commanded by 10 generals, the most daring of whom was Miltiades. While the Persian cavalry was away, he seized the opportunity to attack. The Greeks won a decisive victory, losing only 192 men to the Persians’ 6,400 (according to the historian Herodotus). The Greeks then prevented a surprise attack on Athens itself by quickly marching back to the city.

Sophocles (c. 496 - 406 BCE) and Euripides (c. 484 - 406 BCE), along with Aeschylus (see above), are the three great tragic playwrights of ancient Greece. Euripides' surviving plays are numerous. The best known of Sophocles' 123 dramas, and possibly the best known works of Greed tragedy, are "Oedipus Rex" and "Antigone." Antigone is the daughter of Oedipus, the former king of Thebes. She is willing to face the capital punishment that has been decreed by her uncle Creon, the new king, as the penalty for anyone burying her brother Polyneices. (Polyneices has just been killed attacking Thebes, and it is as posthumous punishment for this attack that Creon has forbidden the burial of his corpse.) Obeying all her instincts of love, loyalty, and humanity, Antigone defies Creon and dutifully buries her brother’s corpse. Creon, from conviction that reasons of state outweigh family ties, refuses to commute Antigone’s death sentence. By the time Creon is finally persuaded by the prophet Tiresias to relent and free Antigone, she has killed herself in her prison cell. Creon’s son, Haemon, kills himself out of love and sympathy for the dead Antigone, and Creon’s wife, Eurydice, then kills herself out of grief over these tragic events. At the play’s end Creon is left desolate and broken in spirit. In his narrow and unduly rigid adherence to his civic duties, Creon has defied the gods through his denial of humanity’s common obligations toward the dead. The play thus concerns the conflicting obligations of civic versus personal loyalties and religious mores.

Living about the same time as Sophocles and Euripedes (as well as contemporaneous with the life of Socrates - see below), from around 495 until 429 BCE, Pericles was an Athenian statesman largely responsible for the full development of both Athenian democracy and the Athenian empire, making Athens the political and cultural focus of Greece. Besides his impressive leadership of the Delian League of Greek city-states, his achievements included the construction of the Acropolis, begun in 447.

Living from about 495 until 430 BCE, Zeno of Elea, founder of the School of Eleaticism, argued that the assumption that there is motion and plurality leads to contradictory consequences. This he did by means of his famous paradoxes, saying that the flying arrow rests since it can neither move in the place in which it is nor in a place in which it is not, and that Achilles cannot outrun a turtle because, when he has reached its starting point, the turtle will have moved to a further point, and so on ad infinitum—that, in fact, he cannot even start running, for, before traversing the stretch to the starting point of the turtle, he will have to traverse half of it, and again half of that, and so on ad infinitum. All of these paradoxes are derived from the problem of the continuum. Although they have often been dismissed as logical nonsense, many attempts have also been made to dispose of them by means of mathematical theorems, such as the theory of convergent series or the theory of sets. In the end, however, the logical difficulties raised in Zeno’s arguments have always come back with a vengeance, for the human mind is so constructed that it can look at a continuum in two ways that are not quite reconcilable. Most importantly, Zeno developed the Reductio ad Absurdum as the standard method for the "indirect proof" of deductive logic. This is the technique of drawing an obviously false, absurd, or impossible conclusion from an assumption, thus demonstrating that the assumption cannot be true. Considered by Aristotle to be the father of the dialectic, Zeno's argument against motion (also known as "Zeno's Paradox") was profoundly influential to the development of a theory of mathematical limits, transfinite numbers, and modern analysis.

In 494 BCE, after being worn down by military service, bad economic conditions, and the rigours of early Rome’s debt law, the plebeians in 494 BCE seceded in a body from the city to the Sacred Mount, located three miles from Rome. There they pitched camp and elected their own officials for their future protection. Because the state was threatened with an enemy attack, the Senate was forced to allow the plebeians to have their own officials, the Tribunes of the Plebs. The tribunes had no insignia of office, like the consuls had, but they were regarded as sacrosanct. Whoever physically harmed them could be killed with impunity. They had the right to intercede on a citizen’s behalf against the action of a consul, but their powers were valid only within one mile from the pomerium. They convoked the tribal assembly and submitted bills to it for legislation. Tribunes prosecuted other magistrates before the assembled people for misconduct in office. They could also veto the action of another tribune (veto meaning “I forbid”). Two plebeian aediles served as their assistants in managing the affairs of the city. Although they were thought of as the champions of the people, persons elected to this office came from aristocratic families and generally favoured the status quo. Nevertheless, the office could be and sometimes was used by young aspiring aristocrats to make a name for themselves by taking up populist causes in opposition to the nobility.

Living from about 490 until 430 BCE, Empedocles of Acragas, a student of the School of Atomism, argued that there are four material elements, air, earth, fire, and water (he called them the roots of everything) and two forces, love and hate, that did not come into being and would never pass away, increase, or diminish. But the elements are constantly mixed with one another by love and again separated by hate. Thus, through mixture and decomposition, composite things come into being and pass away. Because Empedocles conceived of love and hate as blind forces, he had to explain how, through random motion, living beings could emerge. This he did by means of a somewhat crude anticipation of the theory of the survival of the fittest. In the process of mixture and decomposition, the limbs and parts of various animals would be formed by chance. But they could not survive on their own; they would survive only when, by chance, they had come together in such a way that they were able to support and reproduce themselves. It was in this way that the various species were produced and continued to exist. This philosophy later influenced Charles Darwin in his derivation of the Theory of Evolution.

Living from about 500 until 428 BCE, Anaxagoras of Clazomenae, also a student of the School of Atomism, argued that because nothing, by definition, can never exist, everything must be contained in everything else, but in the form of infinitely small parts. In the beginning, all of these particles had existed in an even mixture, in which nothing could be distinguished, much like the indefinite apeiron of Anaximander. But then nous, or intelligence, began at one point to set these particles into a whirling motion, foreseeing that in this way they would become separated from one another and then recombine in the most various ways so as to produce gradually the world in which human beings live. In contrast to the forces assumed by Empedocles, the nous of Anaxagoras is not blind but foresees and intends the production of the cosmos, including living and intelligent beings; however, it does not interfere with the process after having started the whirling motion. This is a strange combination of a mechanical and a non-mechanical explanation of the world.

Living from about 490 until 420 BCE, Protagoras of Abdera argued that “man is the measure of all things, of those which are that they are and of those which are not that they are not.” For human beings the world is what it appears to them to be, not something else; Protagoras illustrated his point by saying that it makes no sense to tell a person that it is really warm when he is shivering with cold because for him it is cold—for him, the cold exists, is there. This belief was later reformulated in modern times as the Anthropic Principle. Plato was sufficiently influenced by Protagoras that he named one of his dialogues after him.

Herodotus (living from about 484 BCE and until sometime between 430 and 420 BCE) and Thucydides (living from around 460 BCE until sometime after 404 BCE) are considered by many to be the two greatest historians of ancient times, particularly for establishing the historical narrative in an objective format. Herodotus is commonly called the father of history and his "History" contains the first truly literary use of prose in Western literature. Of the two, Thucydides was the more careful historian. His critical use of sources, inclusion of documents, and laborious research made his History of the Peloponnesian War a significant influence on later generations of historians.

Living from about 483 until 376 BCE, Gorgias of Leontini challenged the contemporary wisdom of the Greek philosophers in his book Peri tou mē ontos ē peri physeōs (“On That Which Is Not; or, On Nature”), in which — referring to the “truly existing world,” also called “the nature of things” — he attempted to prove that: (1) nothing exists; (2) if something existed, one could have no knowledge of it; and (3) that if nevertheless somebody knew something existed, he could not communicate his knowledge to others. As such, Gorias is considered the Father of the modern Philosophy of Skepticism.

In 480 BCE, at the Battle of Thermopylae, a hugely out-numbered army of 7,000 Spartan hoplites defeated the Persian army of Xerxes I at the pass of Thermopylae, Greece. The Persian navy was defeated by the Athenian navy, under the command of Themistocles, at Artemisiam and Salamis. Then, in 479 BCE at the Battle of Plataea, the Persian army under Xerxes I was driven out of Greece, where it was defeated by a combined force of Spartans, Tegeans, and Athenians. The Persian navy was then defeated at Mycale, on the Asiatic coast, when it declined to engage the Greek fleet. Instead, the Persian navy beached its ships and, joining a land army, fought a losing battle against a Spartan force led by Leotychidas.

In 478 BCE, the Delian League, a confederacy of ancient Greek states under the leadership of Athens, with headquarters at Delos, was founded as a consequence of the Greco-Persian wars. The original organization of the league, as sketched by Thucydides, indicated that all Greeks were invited to join to protect themselves from Achaemenian Persia. In fact, Athens was interested in further supporting the Ionians in Anatolia and exacting retribution from the Persians, whereas Sparta was reluctant to commit itself heavily overseas. Athenian imperialism continued as an increasingly aggressive foreign policy until Sparta put a stop to this expansion and destroyed the Athenian Empire in the Peloponnesian War of 431-404 BCE.

Meanwhile, in Rome in 471 BCE, the number of Roman plebian tribunes was increased to five. The Concilium Plebis was established in support of popular government, as a political counterweight to the power traditionally expressed by the aristocratic patricians in the Senate. The Concilium Plebis was organized and voted by way of the historical Roman tribes. It consisted exclusively of plebeians and could be summoned and presided over only by the plebeian magistrates - i.e., the tribunes.

From about 460 until 375 BCE, Hippocrates of Cos, an ancient Greek physician, lived during Greece’s Classical period and is traditionally regarded as the father of the discipline of Medicine. He has been revered for his ethical standards in medical practice, mainly for the Hippocratic Oath, which, it is suspected, he did not write. Also during this time, Leucippus of Miletus attempted to solve the Parmenidean Problem. Leucippus found the solution in the assumption that, contrary to Parmenides’ argument, nothing does in a way "exist" — as empty space. There are, then, two fundamental principles of the physical world, empty space and filled space — the latter consisting of atoms that, in contrast to those of modern physics, are real atoms; that is, they are absolutely indivisible because nothing can penetrate to split them. Also, during this time, Democritus of Abdera built, on the foundations laid by Leucippus, a whole system aimed at a complete explanation of the varied phenomena of the visible world by means of an analysis of its atomic structure. This system began with elementary physical problems, such as why a hard body can be lighter than a softer one. The explanation given was that the heavier body contained more atoms, which are equally distributed and of round shape; the lighter body, however, had fewer atoms, most of which had hooks by which they formed rigid gratings. The system ended with educational and ethical questions. For example, it was posited that a sound and cheerful person, useful to his fellows, was literally well-composed. Although destructive passions involved violent, long-distance atomic motions, education could help to contain them, creating a better composure. Democritus also developed a theory of the evolution of culture, which influenced later thinkers. Civilization, he thought, was produced by the needs of life, which compel human beings to work and to make inventions. When life becomes too easy because all needs are met, there is a danger that civilization will decay as people become unruly and negligent. Democritus' theory had a profound influence on Thomas Dalton's derivation of his now universally accepted Atomic Theory of Matter.

In 457 BCE, the number of Roman plebeian tribunes was increased to ten. Around 451 to 450 BCE, the Twelve Tables were enacted in Rome during the struggle of the plebeians for political equality. They represented an effort to obtain a written and public code that patrician magistrates could not alter at will against plebeian litigants. Little is known of the actual content of the Twelve Tables; the text of the code has not survived, and only a few fragments are extant, collected from allusions and quotations in the works of authors such as Cicero. From the fragments, it is apparent that numerous matters were treated, among them family law, delict (tort, or offense against the law), and legal procedure.

Meanwhile in Greece, and living from about 450 until about 388 BCE, Aristophanes wrote the greatest of the Greek comedies, of which eleven plays survive. These are a treasure trove of comic presentation in which he poked fun at everyone and every institution. For boldness of fantasy, for merciless insult, for unqualified indecency, and for outrageous and free political criticism, there is nothing to compare to the comedies of Aristophanes. In The Birds, he held up Athenian democracy to ridicule. In The Clouds, he attacked the philosopher Socrates. In Lysistrata, he denounced war.

Beginning in 447 BCE, two quaestors were elected as financial officials of the consuls of Rome, and their number was increased to four in 421 BCE. In 445 BCE, the Lex Canuleia was also enacted, permitting the plebeian citizens of Rome to marry patrician citizens. In addition, the position of Military Tribune with Consular Powers was created. The annalistic tradition portrayed this innovation as resulting from a political compromise between plebeian tribunes, demanding access to the consulship, and the Senate, trying to maintain the patrician monopoly of the office. Henceforth, each year the people were to decide whether to elect two patrician consuls or military tribunes with consular power who could be patricians or plebeians. The list of magistrates for 444 to 367 BCE shows that the chief magistracy alternated between consuls and military tribunes. Consuls were more frequently elected down to 426 but rarely thereafter. At first there were three military tribunes, but the number increased to four in 426, and to six in 406. The consular tribunate was abolished in 367 BCE and replaced by the consulship. The increase in the number of military tribunes coincided with Rome’s first two major wars, against Fidenae and Veii.

Beginning in 443 BCE, two censors were elected in Rome about every five years and held office for 18 months. They drew up official lists of Roman citizens, assessed the value of their property, and assigned them to their proper tribe and century within the tribal and centuriate assemblies.

Around 440 BCE, Hippocrates of Chios, a Greek geometer, compiled the first known work on the elements of geometry nearly a century before Euclid. Although the work is no longer extant, Euclid may have used it as a model for his work the Elements.

From 437 until 426 BCE, Rome fought their first war with an organized, neighboring city-state, Fidenae, and eventually conquered them. From 431 until 404 BCE, Athens fought Sparta in the Peloponnesian War, a nearly thirty year struggle in which Sparta and Athens, under the leadership of Pericles, vied for preeminence in the Aegean, and which ended with Athens' ultimate defeat and the dismantling of the Athenian Empire.

Living from 428/427 until 348/347 BCE, Plato, a student of Socrates, wrote his Dialoges, becoming probably the most influential philosopher of Western Civilization. Through his Dialogues, in which Socrates is the protagonist, he was the first to explicitly state the philosophical foundations of logic: (1) What is it that can properly be called true or false? (2) What is the nature of the connection between the assumptions of a valid argument and its conclusion? (3) What is the nature of definition? In his most famous dialogue, the Republic, Plato stated a complete (if not controversial) theory of government that would have a profound influence on the development of Western Civilization. Plato also formulated an ethical theory of the "common good" which was to guide the development of moral philosophy for the next two thousand years. The teacher of Aristotle, Plato's numerous writings are considered to form the "cornerstone" of the Western Philosophical Tradition.

In 423 BCE, Aristophanes described the lensing properties of glass and other translucent materials. From 406 until 396 BCE, Rome fought and destroyed the neighboring Etruscan city of Veii, ushering in the ultimate extinction of Etruscan culture. From 404 until 343 BCE, the Egyptians are effectively liberated from Persian rule after the death of Darius II until the reconquest of Egypt by the Persians in 343 BCE.

The "third historian" of ancient Greece, Xenophon, began his "Hellenica" where Thucydides ended his work about 411 BC and carried his history to 362 BC. His writings were superficial in comparison to those of Thucydides, but he wrote with authority on military matters. He therefore is at his best in the Anabasis, an account of his participation in a Greek mercenary army that tried to help the Persian Cyrus expel his brother from the throne. Xenophon also wrote three works in praise of the philosopher Socrates: Apology, Symposium, and Memorabilia. Although both Xenophon and Plato knew Socrates, their accounts are very different, and it is interesting to compare the view of the military historian to that of the poet-philosopher.

Around 400 BCE, Siddhartha Gautama, also known as the Buddha, is born somewhere in Northern India. The title buddha was used by a number of religious groups in ancient India and had a range of meanings, but it came to be associated most strongly with the tradition of Buddhism and to mean an enlightened being, one who has awakened from the sleep of ignorance and achieved freedom from suffering. According to the various traditions of Buddhism, there have been buddhas in the past and there will be buddhas in the future. Some forms of Buddhism hold that there is only one buddha for each historical age; others hold that all beings will eventually become buddhas because they possess the buddha nature (tathagatagarbha).

Also around 400 BCE, Thrasymachus of Chalcedon declared openly that “right is what is beneficial for the stronger or better one” — that is, for the one able to win the power to bend others to his will — a statement that profoundly influenced the philosophy of Friedrich Nietzsche and, in a much later and ironic twist of fate, the policies of the Nazi Party in Germany, with dire consequences.

In 399 BCE, Socrates, acknowledged by some to be the Father of Western Civilization, is executed in Athens by drinking hemlock. The Apology, one of the most influential books ever written in Western culture, is an account of Socrates' oratory given to the people of Athens in his defense. From 384 - 322 BCE, Aristotle, a student of Plato, lived and was the first philosopher to attempt a systematic analysis of logical syntax using ordinary grammar, with nouns (or terms) and a linking verb (or copula) in what we now call Propositional Logic. Although Aristotle's fundamental theory of logic is sound, he did not fully distinguish between the truth of the predicate terms and the truth of the subject propositions. Aristotle was the tutor of Alexander the Great and the subjects of his writings range across the entire spectrum of ancient knowledge and attempt a complete description of the natural world, as it was known at that time. The emphasis on Platonic thinking, as exemplified and amplified by Aristotle, is that the Universe can be described by a few, unified, natural laws that can be determined only through careful, thorough, and exacting philosophical explorations. Among other things, Aristotle hypothesized that light is a wave-form disturbance in the "element" of air. He also made a comprehensive compilation of the knowledge of Nature known at that time that is still available in its entirety, as well as treatises on ethics and political philosophy that remain influential today.

In 390 BCE, Gallic tribes sacked the city of Rome, an event which will not happen again for nearly 800 years. In 381 BCE, Rome absorbed the neighboring region of Tusculum by giving Roman citizenship to the inhabitants. In 367 BCE, a law reinstating the consulship instead of the military tribunes with consular power was one of three tribunician bills, the so-called Licinio-Sextian Rogations, passed that year. Another forbade citizens to rent more than 500 iugera (330 acres) of public land, and the third provided for the alleviation of indebtedness.

In 366 BCE, according to the annalistic tradition, the first plebeian consul was elected. All consuls before that time were thought to have been patrician, and one major aspect of the struggle of the orders was supposed to have been the plebeians’ persistent agitation to make the office open to them. However, if the classification of patrician and plebeian names known for the middle and late republic is applied to the consular list for the years 509–445 BCE, plebeian names are well represented (30 percent). Therefore, it is likely that there never was an actual prohibition against plebeians holding the consulship. The distinction between patrician and plebeian families may have become fixed only by the middle of the 4th century BCE; and the law of that time (367 BCE), which specified that one of the consuls was to be plebeian, may have done nothing more than to guarantee legally that both groups of the nobility (which now contained both patrician and plebian families) would have an equal share in the state’s highest office. In addition, six undifferentiated military tribunes were replaced with five magistrates that had specific functions: two consuls for conducting wars, an urban praetor who handled lawsuits in Rome, and two curule aediles who managed various affairs in the city. In 362 BCE, the Romans began to annually elect six military tribunes as subordinate officers of the consuls.

Around 360 BCE, a philosophy that its author called Skepticism was initiated by Pyrrhon of Elis (c. 360-272 BCE), Skepticism was destined to become of great importance for the preservation of detailed knowledge of Hellenistic philosophy in general. Pyrrhon had come to the conviction that no one can know anything for certain, nor can he ever be certain that the things he perceives with his senses are real and not illusory. Pyrrhon is said to have carried the practical consequences of his conviction so far that, when walking in the streets, he paid no attention to vehicles and other obstacles, so that his faithful disciples always had to accompany him to see that he came to no harm. Pyrrhon’s importance for the history of philosophy lies in the fact that one of the later adherents of his doctrine, Sextus Empiricus (flourished 3rd century C.E.), wrote a large work, Pros dogmatikous (“Against the Dogmatists”), in which he tried to refute all of the philosophers who held positive views, and in so doing he quoted extensively from their works, thus preserving much that would otherwise have been lost. It is a noteworthy fact that the British empiricists of the 18th century, such as David Hume (1711–76), as well as the idealist Immanuel Kant (1724–1804) (who was highly critical of the Empiricists), derived most of their knowledge of ancient philosophy from Sextus Empiricus.

Around 359 BCE, Phillip II of Macedon took the throne. In 358 BCE, Rome created two more rustic tribes for the Roman assemblies from territory captured along the Volscian coast, thereby absorbing that territory. Also in 358 BCE, Phillip II of Macedon defeated the Illyrians and consolidated his power in Macedonia.

In 357 BCE, the Comitia Populi Tributa is founded in imitation of the Comitia Plebis, but differed from the latter in that it was an assembly of the whole Roman people, plebeians and patricians. In 348 BCE, after the Gallic Sack of Rome in 390 BCE, the Romans fought almost continuously to regain their predominance among the other Latin tribes, eventually culminating in their second treaty with Carthage.

From 343 until 332 BCE, the Persians, under Artaxerxes III, reestablished control over Egypt until Ancient Egypt's final conquest by Alexander the Great in 332 BCE, effectively ending Egypt's final dynasty and ushering in a period of rule by the Greek-influenced Ptolemaic Kings and Queens of Egypt, who finally succumb to incorporation into the Roman Empire by Cesar Augustus about 30 BCE. From 343 until 341 BCE, Rome's First Samnite War resulted in the major acquisition to the Roman state of the rich land of Campania with its capital of Capua.

Living from 341 until 270 BCE, Epicurus argued that the purpose of philosophy was to attain the happy, tranquil life, characterized by ataraxia — peace and freedom from fear — and aponia — the absence of pain — and by living a self-sufficient life surrounded by friends. He taught that pleasure and pain are the measures of what is good and evil, that death is the end of the body and the soul and should therefore not be feared, that the gods do not reward or punish humans, that the universe is infinite and eternal, and that events in the world are ultimately based on the motions and interactions of atoms moving in empty space. Because it first stated the principle that all organisms seek pleasure and avoid pain, Epicureanism had a great influence on the later development of the psychological philosophy of Behaviorism.

From 340 until 338 BCE, Rome fights what has been called the Latin War. Since the Gallic sack of Rome in 390 BCE, Rome had become increasingly dominant within the Latin League. The absorption of Campania provoked the Latins to take up arms against Rome to maintain their independence. However, the war was quickly decided in Rome’s favour. Virtually all of Latium was given Roman citizenship and became Roman territory, but the towns retained their local governments. The large states of Praeneste and Tibur maintained nominal independence by becoming Rome’s military allies. Thus the Latin League was abolished; but the legal rights that the Latins had enjoyed among themselves were retained by Rome as a legal status, the Latin right (ius Latii), and used for centuries as an intermediate step between non-Roman status and full Roman citizenship.

Around 335 BCE, stating one of the loftiest and most sublime philosophies in the record of Western civilization, the Stoics urged an active participation in human affairs. The Stoics believed that the goal of all inquiry is to provide a mode of conduct characterized by tranquillity of mind and certainty of moral worth. One of the Stoics' most important contributions was to the newly developing study of science by the creation of the first system of a formal (symbolic) logic. They did this primarily by distinguishing between the meaning or truths of the predicate terms and the subject propositions represented by those terms. They were the first to derive the rigorous statement of the conditional term (the "if-then" statement) and the truth table for those statements are considered correct by modern logicians; and they distinguished the modality of arguments as three: (1) the possible (that which either is or will be true); (2) the impossible (that which will not be true); and (3) the contingent (that which either is or will be false, as determined by a certain predicate condition).

In 338 BCE, Phillip II of Macedon defeated the Athenians and completed his conquest of Greece. In 336 BCE, Alexander the Great, a student of Aristotle, acceded to the throne after the assassination of his father, Phillip II of Macedon, that same year. In 335 BCE, Alexander consolidated his power in the Balkans and Greece in his Balkan Campaign. Alexander's subsequent campaigns against the Persian Empire brought it to defeat after the assassination of the last Persian Emperor, Darius III. In the autumn of 332 BCE, during his campaign against Persia, Alexander invaded Egypt with his mixed army of Macedonians and Greeks and found the Egyptians ready to throw off the oppressive control of the Persians. Alexander was welcomed by the Egyptians as a liberator and took the country without a battle. By 323 BCE, Alexander had conquered Asia and the Middle East as far East as India and Pakistan (including Egypt), ushering in the era of the Hellenistic, Ptolemaic kingdoms in the various regions of his conquest when his sons succeeded him after his death in the City of Babylon in 323 BCE. In Egypt, the Ptolemaic Kings and Queens governed Egypt until the conquest of Egypt by Augustus Caesar of Rome in 30 BCE.

From 326 until 304 BCE, Rome fought the Second Samnite War. During this war, Rome succeeded by abandoning the phalanx system of hoplite warfare learned from the Etruscans (who learned this from the Greeks) and adopted the manipular formations by which the Samnites had greatly succeeded in the first half of the Second War. The manipular formation resembled a checkerboard pattern, in which solid squares of soldiers were separated by empty square spaces. It was far more flexible than the solidly massed hoplite formation, allowing the army to maneuver better on rugged terrain. The system was retained throughout the Republic and into the Empire. During these same years Rome organized a rudimentary navy, constructed its first military roads (construction of the Via Appia was begun in 312 BCE and of the Via Valeria in 306), and increased the size of its annual military levy as seen from the increase of annually elected military tribunes from 6 to 16. During the period of 334 to 295 BCE, Rome founded 13 colonies against the Samnites and created six new rustic tribes in annexed territory. During the last years of the war, the Romans also extended their power into northern Etruria and Umbria. Several successful campaigns forced the cities in these areas to become Rome’s allies. The "Great Samnite War" finally ended in Rome’s victory.

In 323 BCE, the Hellenistic Seleucid Dynasty is established after the death of Alexander the Great and reigns until the accessian of the Parthian Kingdom in 247 BCE. In 304 BCE, the Fasti Consulares were first exhibited in the Roman Forum by the aedile Gnaeus Flavius, who broke a patrician monopoly on their use. This also permitted a somewhat reliable and, most-importantly, wide-spread dating of years from the date of the supposed founding of Rome, rather than simply referring to the relative year of a reigning consul, which limited historical perspective to one's own lifetime.

Around 300 BCE, Euclid of Alexandria is born. Euclid was the first to use demonstrative, deductive logic to lay out a complete foundation and derivation of elementary geometric principles when he stated and utilized the "three basic principles of geometry" (which later were applied as the three foundational principles of any logical/mathematical system): (1) that certain propositions must be accepted as true without demonstration (i.e., "first principles," axioms, or postulates); (2) that all other propositions of the system are derived from first principles; and (3) that the method of derivation must be formal -- i.e., independent of the particular subject matter in question. As such, Euclid is considered to be the "Father of Geometry." He also studied the properties of reflection and noted that "things seen under a greater angle appear greater, and those under a lesser angle less, while those under equal angles appear equal". In the 36 logical propositions that he derived, Euclid related the apparent size of an object to its distance from the eye and investigated the apparent shapes of cylinders and cones when viewed from different angles.

Around 300 BCE, the ancient Greek Explorer Pytheas of Marseilles explored the region around the British Isles. Also around this time, Proto-Mongolic is spoken in Mongolia and the Yayoi Culture begins in Japan and lasts until about 250 C.E. It is characterized by bronze and iron casting. They wove hemp and lived in village communities of thatched-roofed, raised-floor houses. They employed a method of wet paddy rice cultivation, of Chinese origin, and continued the hunting and shell-gathering economy of the Jōmon culture. Also around 300 BCE, a student of Aristotle, published many treatises on the sciences and the history of philosophy, including a method for smelting Mercury from the mineral cinnabar.

From 298 until 290 BCE, the Third Samnite War was the last desperate attempt of the Samnites to remain independent Rome. They persuaded the Etruscans, Umbrians, and Gauls to join them. Rome emerged victorious over this formidable coalition at the battle of Sentinum in 295 BCE and spent the remainder of the war putting down lingering Samnite resistance. The Samnites, Umbrians, and Etruscans were henceforth bound to Rome by a series of alliances and Rome had gained complete control of the central Italian peninsula.

From around 290/280 to 212/211 BCE, Archimedes of Syracuse lived and is considered by many to be the most famous mathematician and inventor of ancient Greece. Archimedes was especially important for his discovery of the relation between the surface and volume of a sphere and its circumscribing cyclinder. He is known for his formulation of a hydrostatic principle (known as Archimedes’ principle) and a device for raising water, still used in developing countries, known as the Archimedes screw. He is also famous for his very accurate calculation of the Earth's circumference by measuring the variation in shadow lengths for the same height object at different latitudes, and for his famous saying about the principal of leverage, "if I had a lever, I could move the world."

In 287 BCE the social legislation of the Lex Hortensia was enacted in Rome. Until 287 BCE, the plebeians waged a campaign (Conflict of the Orders) to have their civil disabilities abolished. They organized themselves into a separate corporation and withdrew from the state on perhaps as many as five or more critical occasions to compel patrician concessions; such a withdrawal was termed a secessio. The plebeian corporation held its own assemblies (concilia plebis), elected its own officials (tribunes and plebeian aediles), who were usually more well-to-do plebeians, and kept its own records. An important step in the plebeian campaign was the achievement of inviolability of their tribunes. The Conflict of the Orders was finally resolved in the final secession of 287 BCE when a plebeian dictator, Quintus Hortensius, was appointed. He instituted a law (Lex Hortensia) making plebiscita (measures passed in the plebeian assembly) binding not only on plebeians but also on the rest of the community. This effectively converted the Cocilium Plebis into the Concilium Plebis Tributa and its simpler procedures and the availability of tribunes made this comitia an important legislative body of the middle and later periods of Republican Rome. Its judicial functions, however, were basically limited to fines for noncapital offenses. Both the Comitia Plebis Tributa and the Comitia Populi Tributa became increasingly influenced by radical tribunes or other demagogic leaders from the period of the Gracchi (c. 130 bc) onward.

From 280 until 275 BCE Rome fought the Pyrrhic War and thereby gained control of most of the Italian Peninsula. Started by a quarrel between the Greek city of Thurii and a Samnite tribe, Thurii called upon the assistance of Rome, whose naval operations in the area provoked a war with the Greek city of Tarentum. As in previous conflicts with Italian peoples, Tarentum summoned military aid from mainland Greece, calling upon King Pyrrhus of Epirus, one of the most brilliant generals of the ancient world. Pyrrhus arrived in southern Italy in 280 BCE with 20 elephants and 25,000 highly trained soldiers. After defeating the Romans at Heraclea and stirring up revolt among the Samnites, he offered peace terms that would have confined Roman power to central Italy. When the Senate wavered, Appius Claudius, an aged blind senator, roused their courage and persuaded them to continue fighting. Pyrrhus again defeated the Romans in 279 at Asculum. His losses in the two battles numbered 7,500 (almost one-third of his entire force). When congratulated on his victory, Pyrrhus, according to Plutarch, “replied . . . that one other such would utterly undo him.” This type of victory has since been referred to as Pyrrhic victory. Pyrrhus then left Italy and aided the Greeks of Sicily against Carthage; he eventually returned to Italy and was defeated by the Romans in 275 BCE at Beneventum. He then returned to Greece, while Rome put down resistance in Italy and took Tarentum itself by siege in 272. Rome was now the unquestioned master of the Italian peninsula South of the Po River.

Living from 276 until 194 BCE, Eratosthenes of Cyrene was a Greek scientific writer, astronomer, and poet, who made a reasonably accurate measurement of the size of Earth for which any details are known. Also living about this time on the Indian Subcontinent, King Ashoka reigned from around 273/265 to 238/32 BCE. Ashoka's vigorous patronage of Buddhism during his reign furthered the expansion of that religion throughout India. Following his successful but bloody conquest of the Kalinga country on the east coast, Ashoka renounced armed conquest and adopted a policy that he called “conquest by dharma” (i.e., by principles of right life). In order to gain wide publicity for his teachings and his work, Ashoka made them known by means of oral announcements and by engravings on rocks and pillars at suitable sites. These inscriptions—the rock edicts and pillar edicts (e.g., the lion capital of the pillar found at Sarnath, which has become India’s national emblem), mostly dated in various years of his reign—contain statements regarding his thoughts and actions and provide information on his life and acts. His utterances rang of frankness and sincerity.

From 264 until 241 BCE, Rome engaged Carthage in the First Punic War, ultimately expelling the Carthiginians from Sicily and Corsica and attaining control over those two strategic islands. Around 250 BCE, Aristarchus of Samos proposed a model of the solar system in which the Sun is at the center, rather than the Earth, thus presaging the Copernican Revolution in Astronomy by nearly two thousand years. From 247 BCE until 224 CE, the Parthian Empire governed the area of the Iranian Plateau and most of the Middle East until accession to power of the Sasanian Dynasty. In 241 BCE, Sicily becomes Rome's first gubernatorial province.

In 238 BCE, Rome committed a gross breach of their treaty with Carthage when they sent a force to occupy Sardinia, whose insurgent garrison had offered to surrender the island. To the remonstrances of Carthage the Romans replied with a declaration of war and only withheld their attack upon the cession of hostilities by Carthage in Sardinia and Corsica and the payment of a further indemnity. In that same year, the islands of Sardinia and Corsica become Rome's second gubernatorial province. Finally, from 218 until 201 BCE, Rome engaged Carthage in the Second Punic War, ultimately conquering Carthage and attaining control over the entire Western Mediterranean.

Around 200 BCE, Apollonius of Perga wrote the earliest known, comprehensive treatise on the subject of conic sections, which is considered by many to be one of the greatest mathematical treatises ever written. Around the same time, Eumenes II of Pergamon brought his small kingdom to the peak of its power and did more than any other Attalid monarch to make Pergamon a great centre of Greek culture in the East. Most notably, he was the first to use vellum parchment (instead of papyrus scrolls) for the books of a major library.

From 200 until 146 BCE, Rome fought and won several wars against the Greeks, eventually annexing all of Macedon as the first province of what would eventually become Rome's domination of the Western world. Also during this time, Rome is consolidating its power through a series of wars over land seized in Spain and Northern Italy, which it annexes in 197 BCE as the first of two Roman provinces of "nearer" and "farther" Spain. From about 150 until 130 BCE, Polybius wrote his history of the rise of Rome and of Rome's wars in the East. In 146 BCE, Macedonia constitutes Rome's next two gubernatorial provinces.

In 134 BCE, Rome literally inherited the Kingdom of Pergamon upon the death of Attalus III as the new Roman Province of Asia. In the same year, the last resistance to the Roman colonization of Spain was eliminated by the conquering of Numantia by the general Scipio Africanus the Younger and the Western Roman provinces of "Nearer" and "Farther" Spain were completely pacified. The Roman Republic was now at the historical peak of its power and masters the Mediterranean world.

In June of 133 BCE, Tiberius Gracchus was murdered in the Roman Forum by a conservative faction of senators after he attempted to enforce a radical program of land reform. This assassination is considered by many historians to be the "beginning of the end" of the Roman Republic, which finally fell to the dictatorship of Julius Caesar in 46 BCE. In 121 BCE, after an unsuccessful attempt to revive the land reform bill of his older brother Tiberius, Gaius Gracchus committed suicide on the Aventine Hill after his Popularis party was violently besieged by a faction of the Optimates party in Rome.

In 107 BCE, Gaius Marius established the first professionally paid military in Rome's history, beginning a process that would politicize the military and cause it to serve certain individuals' private interests at the expense of the public good, hastening the fall of the Roman Republic. In 105 BCE, Jugurtha, King of Numidia, revolted against Roman rule in North Africa and was conquered by Sulla after a betrayal by Bocchus I of Mauretania.

From 90 until 89 BCE, a rebellion was waged by Rome’s Italian allies (socii) who, denied the Roman franchise after the murder of Drusus after he had proposed the same, fought for independence, were conquered by Rome, and subsequently received universal Roman citizenship. This set a precedent for later conquests, where Roman citizenship was subsequently used as an inducement to gain control over ruling factions.

From 82 until 79 BCE, Sulla was elected Roman dictator and began his reform of the Roman political system that, ironically, sewed the seeds for the fall of the Roman Republic as a reaction to the conservative retrenchment produced by the Sullan reforms. In 63 BCE, the Romans intervened in the internecine conflicts that existed within the Maccabean ruling class of Judea, effectively consolidating Roman political control over Palestine. On September 23 of that year, Octavian, later known as Augustus Caesar, was born in Rome. In the next year, 62 BCE, Cicero quashed a conspiracy of Roman senators who rebelled against the Sullan reforms. Their leader, Catiline, is tried and executed. The incident is later known as the "Cataline Conspiracy." Three years later, in 59 BCE, Caesar, Pompey, and Crassus formed the First Triumvirate, which marked the beginning of rule by threat of military force, without regard to the ancient Roman tradition of choosing leaders who were freely elected by the Senate with the consent of the people.

Around 50 BCE, the technique of glass blowing was first developed in Syria. Also around this time, Proto-Turkic was spoken somewhere in the Central Eurasian Steppe and Hero of Alexandria studied the reflective and lensing properties of mirrors, noting that, if a ray of light propagates from point A to point B within the same medium, the path-length followed is the shortest possible. Hero also developed the first wind-powered machines and devices utilizing hydraulic and pneumatic principles of operation.

In 49 BCE, Caesar crossed the Rubicon River with his own army and eventually conquered the entire Roman Republic. He then orchestrated his election as dictator in 46 BCE, effectively ending the Roman Republic and ushering in the period of the Roman Empire. On March 15, 44 BCE, Julius Caesar was assassinated by a group of Roman Senators as he entered the Roman Senate.

From 43 until 36 BCE, Antony, Octavian, and Lepidus form the Second Triumvirate and govern Rome until Lepidus was effectively removed from power. Antony and Octavian then went to war against each other over the government of what will become the Roman Empire. In 37 BCE, Herod the Great was installed by the Romans as their client King of Judea and, in 31 BCE, Octavian defeated Mark Antony and the Ptolemaic monarch of Egypt, Cleopatra, at the Battle of Actium and assumed control of Egypt. In 30 BCE, Augustus Caesar, formerly known as Octavian, incorporated Egypt into the Roman Empire, where it remained until its fall to Muslim Arab invaders in 638 C.E. In 27 BCE, Augustus Caeser, formerly Octavian, acceeded to power as the first Emperor of the Roman Empire and commenced the period of the Pax Romana, lasting until 180 BCE and during which the government of Rome became the effective, and largely unchallenged, government of the entire Old World west of Persia.

1 CE - 500 CE

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Around 200 CE, the philosophical school of Neo-Platonism was established by Ammonius Saccas, a latin who had been brought up as a Christian but had abandoned his religion for the study of Plato. Because Ammonius wrote nothing, his philosophy is known only through his famous disciple, Plotinus (205–270). But Plotinus did not publish anything either. His philosophy is known through the Enneads, a collection of his writings arranged by his disciple Porphyry (234–305), who also wrote a biography of Plotinus. Although the philosophy of Plotinus (and Ammonius) was derived from Plato, it used many philosophical terms first coined by Aristotle and adopted some elements of Stoicism as well. Yet it was essentially a new philosophy, agreeing with the religious and mystical tendencies of its time. Plotinus assumed the existence of several levels of Being, the highest of which is that of the One or the Good, which are identical but indescribable and indefinable in human language. The next lower level is that of nous, or pure intellect or reason; the third is that of the soul or souls. There then follows the world perceived by the senses. Finally, at the lowest level there is matter, which is the cause of all evil. The highest bliss available to human beings is union with the One, or the Good, which is attained by contemplation and purification. That this is not a lasting state attained once and for all—like the status of the Stoic wise man, who was supposed never to lose his wisdom—is shown by the fact that Porphyry, in his biography, said that Plotinus had experienced this supreme bliss seven times in his life, whereas he, Porphyry, had experienced it only once. Neo-Platonic philosophy continued to be important to the development of Western thinking well into Sixth Century C.E.

Medieval Civilizations (500 - 1400 CE)

500 - 1000 CE

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1000 - 1400 CE

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Modern Civilizations (1400 CE to the Present)

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Renaissance and Englightenment (1400 - 1750)

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Industrial Revolution (1750 - 1950)

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Information Age (1950 to the Present)


  1. Whereas recent experimental evidence indicates we have good reason to believe that the electromagnetic and strong and weak nuclear forces become unified (i.e., of the same strength and thereby symmetrical) at an energy just above 125 GeV/c2, it is supposed that, because of mutual incompatibilities that exist between the Theory of General Relativity and the Theory of Quantum Mechanics (where the former is used to explain gravity and the latter is used to explain the other three forces), an even higher level of energy is required to unify gravity with the other three forces - maybe as much as the highest energy theoretically possible according to Quantum Mechanics - 2.43 x 1018 GeV/c2. Therefore, it is supposed that, as the Universe came into existence and cooled with expansion, Gravity was the first fundamental force of nature to separate from the others.
  2. Also known as "bubble nucleation."
  3. References to three-dimensional size, although necessary for normal parlance, are misleading since the Big Bang was in fact at least a four-dimensional phenomenon, hypothetically infinite in three-dimensional terms, and existing at its center at every point in what was and is potentially infinite in scope. Although the "known" Universe that we can observe initially appears to be finite in its radius due to the "event horizon" caused by the limiting speed of light, the entire Universe is not conceiveably finite since, otherwise, what would be "outside" except more "universe"? Therefore, when distance scales are mentioned herein, they are measured relative to the smallness of the physical dimensions of the objects described for the known Universe at that time (e.g., there may have been only four Goldstone Bosons existing at the time of creation of the known Universe but there were potentially an infinite number of these particles existing in the entire Universe at this time, not just the part we could observe, which would have been incredibly small). Therefore, it must be understood that any scale of measurement referred to herein exists only in relation to the relative size of the objects described, comprising what would become the known Universe we observe today, although this was also happening everywhere else within something that was and still is potentially infinite in its overall scope. In other words, in the first measurable fraction of a second after the Big Bang, everywhere in the potentially infinite universe was incredibly small.
  4. Because measurements of the Cosmic Background Microwave Radition indicate that the age of the universe is estimated to be about 13.799 billion years, it is a common misconception that the radius of the observable universe must therefore be 13.799 billion light-years. However, this reasoning would only make sense if the flat, static, Minkowski conception of space-time under special relativity was correct. In the real universe, however, spacetime is curved in a way that corresponds to the ever-increasing rate of the expansion of space,h as evidenced by Hubble's law and verified by recent astronomical observations. Therefore, considering the rate at which the expansion of the Universe is increasing, the true size of the observable Universe is estimated to have a radius of about 46 billion light years, rather than the 13.799 billion light years predicted by conventional estimates. Therefore, distances obtained by simply multiplying the speed of light with a cosmological time interval have no real physical significance for very long distances (i.e., such as those beyond the diameter of our own galaxy).
  5. Of course, this estimate is limited to the "Observable Universe." Since the Big Bang could not have originated from solely our own position of observation (otherwise we would be at the very center of the entire Universe, and there is no reason to believe this is the case), we must assume that the entire Universe is much larger than what we can observe. If the Universe is potentially infinite in size (and it is difficult to imagine anything else that is not a "universe") then every point could be considered to be at its "center," at least for observational purposes. However, we will assume, based on empirical evidence, what we can observe is the Universe that was packed into the original bubble nucleation at its beginning, with an understanding that this same observation would occur at any other place from which the Universe could be observed. Ultimately, a truly correct understanding of this seeming paradox depends on a four-dimensional view of the subject, rather than a three dimensional view moving upon the axis of a time line.
  6. At this time, all of what would later become the mass of the Universe existed as an equivalent amount of energy and therefore the Goldstone Bosons had no "rest mass."
  7. And, at this size, many billions of times smaller than the size of an object that is entirely governed by the precepts of the Heisenberg Uncertainty Principle, notions of "movement" and "trajectory" are entirely meaningless.
  8. This is due to the lower energy at which the electroweak symmetry much exist without combination with the Strong Force.
  9. Although the speed of light is a kind of cosmic "speed limit" for all physical phenomenon in the Universe, this speed limit does not pertain to the space-time continuum itself.
  10. This is equivalent to something the size of a golfball expanding to the size of the Earth in the same incredibly small fraction of a second.
  11. Fermi-Dirac Statistics.
  12. The other type of Hadron is the Meson, composed of two quarks each.
  13. There were only trace amounts of Deuterium and Tritium because nearly all the Deuterium had combined to form Helium nuclei, and Tritium is very unstable and quickly decays.
  14. A "solar mass" is the mass of our own Sun.
  15. Stars that end as red giants or ordinary novae produce mainly elements up through Oxygen on the Periodic Table, with a very small amount of heavier elements. However, if an ordinary nova occurs, these elements remain locked up in the white dwarf since only the outer gasses explode and the inner core, consituting the white dwarf, remain intact.
  16. One astronomical unit is the the length of the semi-major axis of the Earth's elliptical orbit around the Sun.
  17. Most paleontologists ignore this first extinction event, which is often not counted among the "six" great extinction events on Earth, and the present-day mass extinction of living organisms is often considered to be the "sixth" great extinction event.
  18. And possibly as early as 2.5 billion years ago.
  19. True, terrestrial plants did not evolve until much later, about 500 million years ago as the first mosses. Aquatic plants evolved later when terrestrial plants returned to the water.
  20. Unlike the soft-bodied animals that leave only indirect evidence, such as their tracks in fossilized mud.
  21. Ironically, "modern" sharks and rays evolved two million years prior to this, about 422 million years ago, as Chondrichthyes, possessing only cartilaginous skeletons and without calcified bones.
  22. Unlike other animals, mammals contain three bones in the middle ear, used to transmit sound vibrations to the neural structures of the cochlea of the inner ear.
  23. Depending on the definition of speciation that is used.
  24. For purposes of this outline, "civilization" is defined to mean a political-cultural unit that is some combination of three basic social institutions: a ceremonial center (a formal gathering place for social and cultural activities), a system of writing, and a city within which the social group expresses their culture. We define "city" to mean any settlement with a cohesive population of at least five hundred persons and organized by some kind of political (which includes religious) system for administering a rule of law. "Rule of law" is defined as a set of social norms that protect the social and economic expectations of those under the jurisdiction of those norms.
  25. However, the dating of the unification of Egypt is a product of later record-keeping and the compilation of earlier records. Consequently, it is now believed by archaeologists that the actual unification probably occurred earlier than this.
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