Prehistoric Time Periods

NOTE: Time periods tend to vary a few million years from science site to science site. This is because the tools used to gauge how old certain types of fossils are always improving and as a result the age estimates get closer and closer to the actual times.  What you see below is based on accumulated evidence of significant geological and biological evolutionary events based on current technologies.

f earth's history were compressed into one calendar year, earth forms, cools and develops an atmosphere during January. Late January into February sees global volcanic activity as oceans fill the great basins. Life begins somewhere in March. All of human history occurs in the last 7 minutes of December 31, and Columbus "discovers" America only 3 seconds before the clock strikes midnight (midnight = today).

Timeline updated March 28, 2012

NOTE: "MYA" = Million Years Ago

Era

Period - Epoch

Time (MYA*)

Archeozoic
(
Archean) era

Rocks, oceans and continental plates form. Simplest, oxygen producing life forms appear (Prokaryotic cells having free floating DNA and no nucleus). Bacteria and Archeans appear. Early atmosphere is poisonous to present-day life.

4500 - 1500

Proterozoic
era

Oxygen builds up in the atmosphere, causing many species of bacteria to disappear and leading an extraordinary explosion Eucaryotic organisms (having cells with nucleus and “organelles”). Organelles are structures within cells that perform specific functions necessary for the evolution of fungi, protists, plants, and animals.

1500 - 545

Paleozoic
era
Cambrian period: This was a time of great geological upheaval, and may have contributed to the Cambrian Explosion, i.e., the rise of most major groups of animals having “hard parts,” such as skeletons, leading to a dramatic diversification of species. Also in this period came the formation of the Burgess Shale which preserved many fossils of animals having "soft-bodies."

545-500

Ordovician period: Proliferation of graptolites, trilobites, primitive fish, coral, etc. Fungi and primitive plants appear on land. Gondwanaland, later to become the southern part of the super continent, Pangaea, drifts over the South Pole, triggering a great Ice Age.

500-438

Silurian period: Atmosphere stabilizes. Large scale glacial melting causes a significant rise in sea level. First jawed fish and coral reefs appear. Vascular plants evolved and proliferated.

438-410

Devonian period: Ferns and seed plants, including trees, appear. Vertebrates (animals having backbones), wingless insects and arachnids (spiders) evolve. Appearance of Ventastega curonica, the earliest known tetrapod (heralding the beginning of the evolution of sea animals, to land animals).

410-355

Carboniferous (coal bearing) period: Spreading of great swamps from which we get our present day coal.

355-290

Permian period: First mammal-like animals appear. Closing of the continents formed one super continent, Pangaea. Earth's greatest known extinction occurs at the end of the Permian, destroying 95% of all species on the planet. The cause of this extinction is thought to have been either multiple impact events or massive volcanism.

290-250

Mesozoic
era
Triassic period: Following the great Permian extinction, the Triassic saw an explosion of new species and the disappearance of earth's polar ice caps. It was the beginning of the age of dinosaurs. First appearance of Theropod dinosaurs such as Coelophysis (See-lo-fi-sis), and marine reptiles such as Plesiosaurus. Birds are thought to have evolved from Theropods. The Triassic ends with a minor extinction and Pangaea begins to break up.

250-205

Jurassic period: Atmosphere hot and dry, no polar ice. appearance of  Appearance of the Sauropod (lizard footed) dinosaurs such as Diplodocus and Apatosaurus, and carnivores such as Allosaurus flourish. Also the first protobirds appear such as Archaeopteryx.

205-135

Cretaceous period: Appearance of ceratopsian (SER-a-tops-e-an: horned face) dinosaurs such as Triceratops. Ceratopsians were ornithischians, or bird-hipped dinosaurs. Tyrannosaurus rex appears. First primates appear. Birds, closely related to modern birds, appear as evidenced by the recent discovery in China's Gansu Province Gansus yumenensis.

Evidence is growing that the Cretaceous ended with the impact of several large objects from space, one being the Chicxulub impact (Gulf of Mexico off Yucatan) that measured about 10 kilometers (6 miles) in diameter. There also is evidence of an even larger impact in the Arabian Sea off the coast of India near Bombay, dating to the same period. Dubbed the "Shiva Crater," this impact was apparently formed by a meteoroid or asteroid possibly 40 Kilometers (25 miles) in diameter. Other possible impacts at this same period were the Boltysh crater in Ukraine and the Silverpit Crater off the east coast of the United Kingdom, deep in the North Sea. The great dinosaurs, as well as most other species on land and in the sea, vanished from the face of the earth.

135-65

Cenozoic
era
(Recent Life)
Tertiary period Paleocene epoch: Cooler climate. Polar ice caps form. In the absence of predator dinosaurs and other large carnivores, small, early mammals diversify and radiate across the continents.

65-55

Eocene epoch: Oldest known fossils of most modern mammals appear. All were small, including the ungulates(hoofed animals).

55-34

Oligocene epoch: Appearance of the first elephants with trunks, early horses, and many grasses.

34-23

Miocene epoch: Warmer climate and the rapid evolution of hoofed animals and larger primates. Controversy surrounds Sahelanthropus tchadensis as to its status as an early hominid ancester to the Australopithecines.

Critics point to the fact that the position of its foramen magnum (the hole at the base of the skull which allows the spinal cord to exit) is positioned farther to the rear than is common in the bipedal hominids. Some suggest that S. tchadensis may be an early ape.

In any case, as evolution would predict, such a transitional feature, i.e., the position of the foramen magnum, would certainly move, over time, from rear to center as a creature evolves from quadrupedal (walking on four legs) to bipedal (walking on two legs) locomotion.

23-5.33

Pliocene epoch: Ape and human lines diverge, triggering the age of the Australopithecines (Southern apes).

5.33-1.8

Quaternary period Pleistocene epoch: Most recent Ice Age. Cool, dry climate caused deforestation and extensive spread of grasslands and savannas. Homo habalis flourishes and is associated with the earliest crude stone tools, marking the beginning of technology. Probably evolving from Homo habalis, Homo erectus appears at 1.6 MYA, and discovers how to make fire. Appearance of Homo sapiens neanderthalensis (Neanderthal man) roughly 1.25 MYA and is associated with the Mousterian industry (crude flake tools).

1.8-0.01

Lower Paleolithic: Crude stone tools associated with Homo erectus. Acheulian industry (uniquely chipped hand ax) begins. Sahara Desert experiences a "pluvial" (long period of steady and seasonal rain). Pluvials appear to have a direct correlation with ice ages.

2.6-0.1

Middle Paleolithic (Neolithic): Saharan pluvial ends. This is the age of the Neanderthal.

0.3-0.03

Upper Paleolithic: Last Ice Age occurs. Cro Magnon appears in Southern France about 35,000 years ago. Neanderthal disappears, and is replaced by (or evolves into) Homo sapiens sapiens (modern man). Animal domestication (dog) begins around 12,000 years ago.

0.05-0.01

Holocene epoch (completely recent): Last Ice Age has ended as we enter the present interglacial period (between Ice Ages). >Homo floresiensis >(may have been a dwarf form of Homo erectus) flourished on the Indonesian island of Flores from possibly 95,000 to 13,000 BCE. Modern humans domesticate plants (agriculture begins). Modern global civilization and technology evolves.

0.01-0

 



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