Antiquity of Humanity
Later Human Evolution:
Homo habilis
Evolution of Humans
Homo habilis
Homo erectus
Archaic Homo sapiens
Homo sapiens sapiens
Homo sapiens neandertalensis
Homo habilis (ca. 2.5-1.6 mya)
Homo habilis was first discovered in 1959 in the
Olduvai Gorge in Tanzania.
A nearly complete skull of H. habilis was discovered in
1972 at Koobi Fora on the shores of Lake Turkana in
Kenya. Its age is estimated at 1.8 million years and its
brain capacity at 800 cc.
Other H. habilis remains have since been discovered at
Olduvai Gorge. There is considerable variation among
the specimens from this era found thus far.
Some anthropologists argue that the variations appear to
indicate that several separate species of humans existed
and competed at the same time in east Africa; other
scientists lump all the individuals together in a single
species.
H. habilis finds
Homo habilis
Homo habilis is the earliest known
species of the genus Homo; that is, the
first human species.
– It existed from approximately 2.5 to 1.6 million
years ago in east Africa.
– Only a few fossil remains have been
discovered so far, but these specimens exhibit
a clear trend toward larger brain size.
– H. habilis brains are about 30% larger than
those of A. africanus.
Homo habilis
Brain size much bigger than Aus. (500-800)
Teeth smaller, thinner enamel, more parabolic
dental arcade.
Skulls rounder, less prognathic, jaw muscles
reduced.
East and South Africa, same time as robusts.
Handyman, associated with Pebble choppers
(more later).
This reconstructed
skull was found in
1972 on the shores of
Lake Turkana.
Represents the oldest
individual human yet
discovered.
Homo habilis
Age:ca. 1.8 million years
Date of Discovery:October 1968
Location:Olduvai Gorge, Tanzania
Sexual Dimorphism
Males were much larger
than females, as shown
by the two skulls at far
right.
The male is pictured on
the left.
Sexual dimorphism in
habilis is expressed in
significant size
differences.
First Stone Tools:
Oldowan Pebble Choppers
Tool Technology
Oldowan Pebble Choppers
rounded pebbles
portions broken to form sharp edge
flakes used for butchering
These crude hand axes and stone flakes could have been manufactured
as needed or as opportunity arose. The fracture lines of stones create a
sharp cutting surface capable of butchering fairly large animals. The photo
above right shows a modern anthropologist skinning a calf with a stone tool
made just as ancient Homo habilis would have done.
Environment
The background of the
photo shows the kind of
environment in which this
earliest-known human
species lived--open bush
and savannah country in
east Africa.
This must must have
been a very challenging
environment, filled with
large predators.
?
Behavior
Meat eating
Home base, food sharing, sexual division
of labor.
Archaeological evidence
– Animal bones and stone tools at sites
(Olduvai)
– Hunting or Scavenging?
"Hunting Hypothesis"
One widely held view of human development has held
that hunting as an activity was the chief driver of
evolutionary change in early humans, as it would have
selected for for certain kinds of intelligence, coordination,
and aggressive behavior
Was Homo habilis a hunter of large game and a
successful competitor with the great predators of Africa-lions, leopards, hyenas? Or was this species an
opportunistic taker of small game and a scavenger?
Present evidence cannot answer the question, but a
scavenging role seems more likely.
The Homo habilis Debate
It was once thought that the evolution of the
genus Homo was an example of anagenesis,
the continual and gradual change of one parent
species into its daughter species in a linear
fashion.
As the fossil record began to expand and more
early human fossils were found dating to the
period between 2 million and 1 million years
ago, some questions as to the validity of this
hypothesis were raised.
Below are two fossils, shown to scale. KNM ER
1813 is to the left, and KNM ER 1470 is to the right.
Originally, both were assigned to the species Homo
habilis, with ER 1470 thought of as male and the
smaller ER 1813 a female in a strongly dimorphic
species. However, the anatomies of the two skulls
differ considerably.
Differences
Note that there is a strong supraorbital torus
(horizontal bar of bone above the eye sockets)
on 1813, whereas the supraorbital torus of 1470
is slight at best, and does not have the
depression behind it that is seen in 1813.
The face of 1470 is longer than 1813's and
1470's upper jaw is square instead of roundedoff.
There is a great discrepancy between the cranial
capacities of the two individuals as well.
– ER 1470 has a cranial capacity of 775cc, where ER
1813 has a cranial capacity of only 510cc (which is
above the australopith average, but well below the
accepted 600cc cutoff for Homo)
Debate
One debate in paleoanthropology today is whether or not
ER 1470, and several other fossils previously identified
as H. habilis, should be grouped into a new species,
Homo rudolfensis.
This classification would acknowledge that ER 1470 and
the other members of Homo rudolfensis differ more from
Homo habilis, sensu stricto ("in the strict sense,"
meaning: as originally defined), than could possibly be
accounted for by variation within a population or between
sexes.
This would place two species of the genus Homo in
Africa during the same time period in addition to two
members of the genus Paranthropus, and, possibly, late
surviving members of the species Australopithecus
africanus.
Far more complicated than the original neat, linear
model.
Homo rudolphensis (KNM-ER 1813)
Homo habilis (KNM-ER 1470)
Differences
Homo rudolfensis
Ca. 1.5 metres
Robust
cc600 – 800 cc
2.4 – 1.6 million years
ago
Eastern Africa
Larger, flatter face
Robust jaw; large
narrow molars
Homo habilis
Height1.0 metres
Physique Relatively long arms
Cranial Volume 500 – 650
Known Date2.0 – 1.6 million
years ago
Distribution Eastern & S? Africa
Skull form Relatively small face;
nose developed
Jaws/Teeth Thinner jaw;
smaller, narrow molars