Social Philosophy Blog
|A NATURAL HISTORY TIMELINE
SPECIAL NOTE: Time periods
will vary a few million years from science site to science site. All such divisions are
estimates based on accumulated evidence of significant geological and
biological evolutionary events.
LET ME HEAR FROM YOU:
Please feel free to question any fact and note any errors in the timeline.
Send your questions, corrections and suggestions to
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 (links restored) *MYA = Million Years Ago
Period - Epoch
|Rocks, oceans and
continental plates form. Simplest, oxygen producing life forms appear (Prokaryotic cells
having free floating DNA and no nucleus).
Archaeans appear. Early atmosphere
is poisonous to present-day life.
4500 - 1500
Oxygen builds up in the atmosphere, causing many species of
bacteria to disappear and leading to an extraordinary explosion
of 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
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
Shale which preserved many
animals having "soft-bodies."
period: Proliferation of
trilobites, primitive fish, coral, etc. Fungi
and primitive plants appear on land. Gondwanaland, later to become the southern part of the
Pangaea, drifts over the South Pole, triggering a great Ice Age.
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
period: Ferns and seed plants, including trees, appear. Vertebrates (animals having
backbones), wingless insects and arachnids (spiders) evolve.
the earliest known
(heralding the beginning of the evolution of sea animals, to
(coal bearing) period: Spreading of great swamps from which we get our present day
period: First mammal-like animals appear. Closing of the continents
formed one super
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.
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
dinosaurs such as
Coelophysis (See-lo-fi-sis), and marine reptiles
Plesiosaurus. Birds are thought to have evolved from
Triassic ends with a minor extinction and Pangaea begins to break up.
Atmosphere hot and dry, no polar ice. Appearance of
Appearance of the
Sauropod (lizard footed) dinosaurs such as
carnivores such as
Allosaurus flourish. Also the first
protobirds appear such as
period: Appearance of
ceratopsian (SER-a-tops-e-an: horned face) dinosaurs such as
ornithischians, or bird-hipped dinosaurs.
rex appears. First
Birds, closely related to modern birds, appear as evidenced by
the recent discovery in China's Gansu Province
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
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.
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.
epoch: Oldest known fossils of most modern mammals appear. All were small, including
ungulates (hoofed animals).
epoch: Appearance of the first elephants with trunks, early horses, and many grasses.
epoch: Warmer climate and the rapid evolution of hoofed animals and larger primates. Controversy
Sahelanthropus tchadensis as to its status as an early
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.
epoch: Ape and human lines diverge as
appear, triggering the age of the
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
Homo erectus appears at 1.6 MYA, and discovers how to make fire. Appearance
Homo sapiens neanderthalensis (Neanderthal man) roughly 1.25
MYA and is
associated with the Mousterian industry (crude flake tools).
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.
Middle Paleolithic (Neolithic):
Saharan pluvial ends. This is the age of the Neanderthal.
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.
epoch (completely recent): Last Ice Age has ended as we enter the present interglacial
period (between Ice Ages).
(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.
Updated March 28, 2012