|
|
 |
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 |
|
|
|
|
