History/Origins/Future of Energy,
Matter, Space, Time, and Life (5 of 7) 

From ~23 Million Years Ago
to ~2 Million Years Ago

(updated August 16, 2009)

Years Ago



~23 million to ~2.6 million ....

Neogene Period
23 Million Years to 2.6 Million Years Ago
"... the continents began the Neogene by crashing into each
other. India continued its slow-moving collision with Asia,
which had already started the giant push-up of the Himalaya
that continues today. Italy pushed into Europe, giving rise to
the Alps. Spain butted France, and the Pyrenees rose. Fault-
ing, stretching, thinning, and lifting created parts of the Rocky,
Sierra Nevada, and Cascade Mountains in North America. 

... The Arctic ice cap grew and thickened. ... Sea levels plum-
meted, exposing land bridges between Africa and Eurasia and
between Eurasia and North America. Eventually, South America
moved north and merged with North America, forming the Isth-
mus of Panama.

Species Spread Out

The continental connections gave animals that had evolved in iso-
lation access to new lands. Elephants and apes wandered from
Africa to Eurasia. Rabbits, pigs, saber-toothed cats, and rhinos
went to Africa. Elephants and rhinos continued across the Bering
Strait to North America. Horses went the other way. Ground sloths
migrated from South America to North America; raccoons scurried
south. Even rodents may have hopped Pacific islands en route to
Australia from Southeast Asia.

As the climate changed, many of the great forests that carpeted the
continents from shore to shore and from Pole to Pole slowly gave
way to grasslands ... Horses evolved stronger, enamel-protected
teeth and flourished. So too did ruminants such as bison, camels,
sheep, and giraffes, whose compartmentalized stomachs are well
adapted to digesting grass. Many of the grazers were quick and
roamed in herds—new tricks for survival out in the open. Their
predators were also forced to adapt.

... Sharks grew and dominated the seas once again. Megalodon,
the biggest shark of all, was nearly 50 feet ... long.

Meanwhile on land, Asian and African apes diverged and then,
several million years later, hominins split from their closest African
ape ancestors, the chimpanzees. Adapted to two-footed walking,
early hominins dropped out of the trees and started to carry food
and tools in their hands. These new species were poised to alter
the planet unlike any other in the centuries to come.

~20 million ....

Mountain ranges (the Cordilleras, the Andes,
the Himalayan range) form; most great groups
of mammals appear essentially modern in form;
opening of Red Sea and Gulf of Aden.

India has merged with Asia.

~18 million ....

Proconsul africanus (woodland ape) appears to be
the best candidate yet discovered to be the origin
point (distant ancestor) from which all modern
species of apes and all hominids--human beings

~16.6 million ....

Steens Mountain Basalts
"... Steens Mountain is a centralised Flood basalt sub-
province of 16.6M year age closely allied to the Col-
umbia River Basalts and lying in southern Oregon. ..."

~15 million ....

Hyenas appear.

Columbia River Basalts
"... perhaps the best known of all the flood basalts.
... the Roza centre twice erupted 700 cubic km
within a few days 15,000,000 years ago, forming
a flow with a length of 190 miles (300km), an area
of 15,400 sq miles (40,000 sq km), while the Po-
mona member flowed an even greater distance of
600km to the Pacific Ocean.

... Snake River Basalts ... ages range from 15myr
at the west ..."

~14 million ....

View of the earth in the middle Miocene:

~13 million ....

Asian great apes, Orangutans, split from African
great ape lineage.

Closest yet to Ancestor of all Great Apes
"...  Pierolapithecus catalaunicus, or its close relative,
may have been the last common ancestor to all living
great apes, including humans ... Like other great apes,
Pierolapithecus had a stiff lower spine and other spe-
cial adaptations for climbing. These features, plus the
fossil's age of about 13 million years, suggest that this
species was probably close to the last great ape an-

... The great apes, which now include orangutans,
chimpanzees, gorillas and humans, are thought to
have diverged from the lesser apes, a group that
contains modern gibbons and siamangs, about 11
to 16 million years ago ..."

~12 million ....

Dryopithecus ("tree ape") may have begun the
evolutionary line that developed into modern apes
and Homo sapiens; Sivapethecus appears, an ape
between life in the trees and life on the ground,
chimpanzee-like feet, orangutan-like face;
Ramapithecus ape appears, a little smaller in
stature than Sivapethecus.

New Hominid 12 Million Years Old Found In Spain,
with 'Modern' Facial Features
"... Researchers have discovered a fossilized face and
jaw from a previously unknown hominoid primate genus
in Spain dating to the Middle Miocene era, roughly 12
million years ago. Nicknamed "Lluc," the male bears a
strikingly "modern" facial appearance with a flat face,
rather than a protruding one. The finding sheds important
new light on the evolutionary development of hominids,
including orangutans, chimpanzees, bonobos, gorillas
and humans.

... the new genus and species, dubbed Anoiapithecus
brevirostris. The scientific name is derived from the
region where the fossil was found (l’Anoia) and also
from its 'modern' facial morphology, characterized by
a very short face. ..."

~10 million ....

Opening of Gulf of California.

~8 million ....

Lineage leading to modern gorillas branched away
from remaining African ape species, the combined
chimpanzee and human line.

Reference to Origins of Humankind, as of 2001
(note-a great deal of information is contained in
this page, and some of the referenced dates are
no longer applicable, due to ongoing discoveries
which are one of the greatest advantages of the
scientific method):

~7 million ....

A fall in sea level cuts off the Mediterranean from
the Atlantic Ocean - over the next 2 million years,
the Mediterranean repeatedly reflooded and dried
out; salt deposits of up to 6,500 feet have been left
in some places.

Ancient skull challenges human origins
"A team of researchers in central Africa say they've uncovered
what appears to be the earliest evidence of the human family
ever found -- a skull, jawbone and teeth between 6 million and
7 million years old.

Scientists say the discovery, unearthed in the Djurab desert of
northern Chad, is of considerable importance.

"This is a very exciting find. It expands our knowledge of early
evolution in a couple of different ways, both in time and in space,"
said Ian Tattersall, an anthropologist at The American Museum
of Natural History. It is the first hominid fossil found in central
Africa. ..."

Sahelanthropus tchadensis

~6 million ....

Orrorin tugenensis
(6 million years ago)*

*Because fossil evidence for Orrorin tugenensis is scant,
a range of dates for when this species lived is not available.
Orrorin tugenensis - If Orrorin tugenensis is truly a hom-
inid as its discoverers describe it, the species is by far
the oldest-known member of the family to which humans
belong. In fact, at 6 million years old, O. tugenensis lived
near the time when genetic analyses suggest our oldest
hominid ancestor split from the oldest ancestor of the
great apes. This means that there's a chance O. tugen-
ensis could be the proverbial "missing link" -- or at least
one of them.

Certain features, like the teeth of O. tugenensis, suggest
this species could even be more closely related to Homo
sapiens than the many Australopithecus species it pre-
dates. Like our molars, the molars of O. tugenensis were
small compared to any of the australopithecine teeth. Their
teeth also had very thick enamel like ours.

Grooves in the femurs of O. tugenensis, presumably points
where muscles and ligaments attached, suggest that the
species was bipedal. Unfortunately, much about this
species, including the suggested close relationship between
it and Homo sapiens, is extremely speculative and hotly

Map of Some of the Pivotal Human Evolution Discoveries

A Walk Through Human Evolution

Walk Like a Man

~5.8 million

Between five and six million years ago, the great
desiccation touched off what scientists call the
Messinian Salinity Crisis--a global chemical
imbalance that triggered a wrenching series of
extinctions and plunged the Earth into an ice age.

~5 million ....

Continents are essentially modern in form; Iceland
volcanic island appears; Atlantic Ocean rises enough
to flood back into the Mediterranean.

~4.4 million

Ardipithecus ramidus
(4.4 million years ago)*

*Because fossil evidence for Ardipithecus ramidus is scant,
a range of dates for when this species lived is not available.
Ardipithecus ramidus was discovered in December 1992.
Although not nearly as old as Orrorin tugenensis, Ar. ramidus
is much more widely accepted by the scientific community
as a hominid than is O. tugenensis, and thus is considered
by some to be the oldest-known hominid.

A partial skeleton and indirect evidence from skeletal frag-
ments indicate that Ar. ramidus may have walked upright.
Although considered to be one of the most primitive hom-
inids, Ar. ramidus shares some novel characteristics with
much later hominids, namely aspects of its teeth. The molars
of Ar. ramidus are smaller than are those of any of the
Australopithecus species.

Other fossils found with Ar. ramidus suggest that it may
have been a woodland forest dweller. This may modify
current theories about why hominids became bipedal in
the first place. Walking upright has typically been linked
to movement onto the savanna:


~4.2 million

Australopithecus anamensis
(4.2 to 3.9 million years ago)

Australopithecus amenesis possesses a mix of advanced
and primitive traits. A partial tibia (the larger of the two
lower leg bones) suggests that A. anamensis probably
walked upright. The teeth of A. anamensis were covered
with a layer of enamel much thicker than that of Ar. ramidus,
suggesting a diet of hard-to-chew foods. The thickened
enamel is also a trait characteristic of all later hominids. In
size and shape, however, the teeth of A. anamensis were
primitive relative to later hominids. A. anamensis probably
lived in open woodland habitats in what is now northern
Kenya and southern Ethiopia.:

~4 million

A. anamensis was walking 4 million years ago.

~3.9 million ....

Australopithecus afarensis
(3.6 to 2.9 million years ago)

Australopithecus afarensis had a very low forehead,
a face that projected far forward (as viewed in profile),
and a very prominent brow ridge. A. afarensis is the
earliest species for which we have reliable brain and
body size estimates, thanks to a rich fossil record for
the species.

The brain of A. afarensis was about one-third the size
of the average modern human brain, or about the same
size as a modern ape's brain. Males and females varied
significantly in body size, with males standing approxi-
mately 4 feet 11 inches tall and weighing 100 pounds
and females standing about 3 feet 5 inches tall and
weighing about 62 pounds. Males also typically had
large crests on top of their skulls; females did not.

The knee and pelvic bone structure of A. afarensis were
very humanlike, leaving no doubt that A. afarensis walked
upright. A. afarensis probably inhabited the savannas and
open woodlands where they likely found fruits, seeds,
and roots

~3.5 million ....

Kenyanthropus platyops
(3.5 to 3.3 million years ago)

Kenyanthropus platyops - although it occupied parts of
Africa at the same time as A. afarensis, K. platyops is
quite distinctive physically and, thus, has been classified
not only as a different species, but belonging to a different

The features that distinguish K. platyops from A. afarensis
include primitive traits like small ear holes and advanced
traits like a relatively flat face and small molars. K. platyops
has been compared most closely with Homo rudolfensis or
Homo habilis, species that lived as many as 1 million years

Similarities between these species might be explained in
terms of convergent evolution, in which two distinct groups
adapt to similar environmental conditions in similar ways,
or by the possibility of a direct ancestral line between
K. platyops and H. rudolfensis or H. habilis.

Indeed, some scientists have placed H. rudolfensis speci-
mens in the genus Kenyanthropus. Others ignore Kenyan-
thropus as a genus altogether, placing K. platyops speci-
mens into the genus Australopithecus, saying that the
species is not different enough to warrant its own genus.
Until the species can be substantiated by more fossil
evidence, many anthropologists will continue to withhold
judgement on its validity and significance:

~3.2 million ....

Walking With Beasts -- Next of Kin
"... Filming Locations: South Africa, and the Great Rift Valley

3,200,000 Years Ago — Late Pliocene — Ethiopia

[featured in this episode]
  • Ancylotherium
  • a tribe of small hominids known as Australopithecus, one of the first apes able
    to walk upright and a close ancestor to humans; Australopithecus has evolved
    to walk upright so as to better maneuver the plains as well as the climb the trees;
    although the Australopithecus looks human, it still only has the mind the size of
    a chimpanzee's
  • an angry male Deinotherium, an ancestor of the modern elephant
    feline predator Dinofelis
  • a young Australopithecus (nicknamed "Blue") tries to fit into the tribe after he is
  • Modern day Elephant (live acted)
  • Giraffe (live acted)
  • Hippopotamus (live acted)
  • Rhinoceros (live acted)
  • Cape Buffalo (live acted)
  • Ostrich (live acted)
  • Flamingo (live acted
  • Vulture (live acted)
  • Jackal (live acted)
  • Dik dik (live acted)
  • Warthog (live acted)
  • Zebra (live acted)

(1 to 3 of 10) Walking With Cavemen
"... 3.2 million years B.C. - Ethiopia

Australopithecus afarensis, and focus on their evolved bipedality
(walking on just rear feet - our legs). More specifically, the story
follows the famous Lucy and her relatives, as they first develop
a leadership conflict following the death of the alpha male due to
a crocodile attack, and then are attacked by a rival troupe. The
attack ends with death of Lucy herself, and her eldest daughter
caring for Lucy's now-orphaned baby (her sibling), as a sign of
the developing humanity in these "apemen". ..."

~3 million ....

Australopithecus africanus
(3 to 2 million years ago)

Australopithecus africanus was nearly identical in body
and brain size to A. afarensis. Like A. afarensis, A. africanus
also showed marked differences in size between males and
females. Although the teeth and jaws of A. africanus were
much larger than modern human teeth, they are still more
similar to ours than to the teeth of apes. The upper and
lower jaws of A. africanus were also fully rounded in front,
like those of modern humans, and their canine teeth were
smaller on average than those of A. afarensis. Australo-
pithecus africanus individuals probably inhabited open
woodlands, where they would have foraged for fruits,
seeds, and roots:

Discovery of a 1.22-meter-tall (four feet) hominid
(ape-man) north of Johannesburg, South Africa:

~2.7 million

Australopithecus aethiopicus
(2.7 to 2.3 million years ago)

Australopithecus aethiopicus may be an ancestor of
two later species, Australopithecus robustus and
Australopithecus boisei. The species has a peculiar
mixture of primitive and highly derived traits relative
to earlier species.

Brain size of A. aethiopicus is comparable to that of
modern apes and the much-earlier A. afarensis. Other
skull traits appear to be novel adaptations, some of
which probably allowed A. aethiopicus to exploit
tougher food sources. The massive face was flat or
concave with no forehead.

A very large sagittal crest (a ridge of bone running
along the top of the skull) and other heavily reinforced
areas of the skull would have provided strong points
of attachment for chewing muscles. Powerful chewing
muscles, paired with the species' extremely large and
thickly enameled molars and premolars, suggest that
A. aethiopicus ate very tough, grainy foods that re-
quired a great deal of processing

~2.6 million ....

The earliest stone tools, thought to be 2.6 million years
old, were found nearby in Gona, Ethiopia:

2.6 Million Years Ago to the Present
"Climate change and the developments it spurs carry the narrative
of the Quaternary, the most recent 2.6 million years of Earth's history.
Glaciers advance from the Poles and then retreat, carving and molding
the land with each pulse. Sea levels fall and rise with each period of
freezing and thawing. Some mammals get massive, grow furry coats,
and then disappear. Humans evolve to their modern form, traipse
around the globe, and make a mark on just about every Earth system,
including the climate.

At the start of the Quaternary, the continents were just about where
they are today, slowing inching here and there as the forces of plate
tectonics push and tug them about. But throughout the period, the
planet has wobbled on its path around the sun. The slight shifts cause
ice ages to come and go. By 800,000 years ago, a cyclical pattern
had emerged: Ice ages last about 100,000 years followed by warmer
interglacials of 10,000 to 15,000 years each. The last ice age ended
about 10,000 years ago. Sea levels rose rapidly, and the continents
achieved their present-day outline.

When the temperatures drop, ice sheets spread from the Poles and
cover much of North America and Europe, parts of Asia and South
America, and all of Antarctica. 

... During warm spells, the ice retreats and exposes reshaped mountains
striped with new rivers draining to giant basins like today's Great Lakes.
Plants and animals that sought warmth and comfort toward the Equator
return to the higher latitudes. 

... Since the outset of the Quaternary, whales and sharks have ruled the
seas, topping a food chain with otters, seals, dugongs, fish, squid, crusta-
ceans, urchins, and microscopic plankton filling in the descending rungs.

On land, the chilliest stretches of the Quaternary saw mammals like mam-
moths, rhinos, bison, and oxen grow massive and don shaggy coats of
hair. ... About 10,000 years ago, the climate began to warm, and most
of these so-called megafauna went extinct. 

... the Quaternary is often considered the "Age of Humans." Homo erectus
appeared in Africa at the start of the period, and as time marched on the
hominid line evolved bigger brains and higher intelligence. The first modern
humans evolved in Africa about 190,000 years ago and dispersed to Europe
and Asia and then on to Australia and the Americas. ...

~2.5 million ........

Australopithecus garhi
(2.5 million years ago)

Australopithecus garhi may represent an evolutionary link
between the genera of Australopithecus and Homo. Circum-
stantial evidence suggests that A. garhi may have been the
earliest tool user. Antelope fossils excavated from the same
site as A. garhi show cut marks made by a stone tool; both
the hominid and antelope fossils are dated at 2.5 million
years old:

Technology being used to eat meat and scrape marrow out
of bones; fossil find, in Addis Ababa, Ethiopia, was of skull
and tooth fragments that may be those of a completely new
hominid - a "missing link" or human-like species with long
arms and long legs.

The scientists have called their new hominid Australopithecus
garhi, after the local word for "surprise". From anatomical
analyses and measurements they argue A. garhi is quite dis-
tinct from A. africanus and from the other hominid species
known to be alive around the same time and may be a crea-
ture that immediately preceded humans:

~2.4 million ........

Oldowan tools are the oldest known, appearing first in the
Gona and Omo Basins in Ethiopia about 2.4 million years
ago. They likely came at the end of a long period of oppor-
tunistic tool usage: even chimpanzees use rocks, branches,
leaves and twigs as tools:

~2.3 million ........

Australopithecus boisei
(2.3 to 1.4 million years ago)

Australopithecus boisei is similar in body and brain size to
A. robustus. Like members of many other Australopithecus
species, males and females of A. boisei showed marked
differences in size. Some features of A. boisei's skull, includ-
ing the large grinding teeth, are even larger than are those of
A. robustus. Certain molars measure up to two centimeters
in length from front to back. A. boisei probably inhabited
mixed woodland and savanna habitats, where individuals
would most likely have eaten foods like nuts and roots:

Homo habilis
(2.3 to 1.6 million years ago)

Homo habilis has been a controversial species since it was
first described in the mid-1960s. Originally, many scientists
did not accept its validity, believing that all specimens should
be assigned either to the genus Australopithecus or to Homo
erectus. Today, H. habilis is widely accepted as a species.

Some scientists, however, still believe that many of the ear-
liest fossils assigned to H. habilis are too fragmented and
separated in time for conclusions about their relationships
or species compositions to be possible. H. habilis speci-
mens with particularly large features -- brains or teeth, for
instance -- are sometimes assigned as Homo rudolfensis.

Homo habilis, "handy man," is so called because of the
wealth of tools that have been found with its fossils. The
average H. habilis brain was considerably larger than the
average Australopithecus brain. The brain shape is also
more humanlike. The bulge of Broca's area, essential for
speech, is visible in one H. habilis brain cast, indicating
that the species may have been capable of rudimentary
speech. The average H. habilis individual is thought to have
been about five feet tall and 100 pounds, although females
may have been smaller:

~2 million ....

(4 of 10) Walking With Cavemen
"... 2 million years B.C. - East Africa

The herbivorous Paranthropus boisei are "a master of one" - i.e.
they are specialized herbivores.  Consequently, Paranthropus
boisei will not be able to survive in the future, when at the begin-
ning of the next Ice Age the climate will change, and their plants
will be gone for good. ..."

--- end 5 of 7 ---