Encyclopedia of Evolution.pdf - Online Reading Center

tions were spreading through Africa. After an initial burst
of evolution anatomical characteristics remained relatively
unchanged. Toolmaking culture also changed little during
that time. Although the tools became thinner, they remained
recognizable members of the Acheulean industry. When H.
ergaster began to evolve into modern humans, about a million
years ago, another rapid period of physical and cultural
evolution began. Not only is H. ergaster itself an almost
perfect example of a “missing link” between H. habilis and
modern humans, but also there are numerous examples of
intermediate forms between H. ergaster and modern humans
in Africa.
Further Reading
Leakey, Richard, and Roger Lewin. Origins Reconsidered: In Search
of What Makes Us Human. New York: Doubleday, 1992.
Potts, R., and Pat Shipman. “Cut marks made by stone tools on
bones from Olduvai Gorge, Tanzania.” Nature 291 (1981): 577–
580.
Tattersall, Ian, and Jeffrey Schwartz. Extinct Humans. New York:
Westview, 2000.
Walker, Alan, and Richard Leakey. The Nariokotome Homo Erectus
Skeleton. Cambridge, Mass.: Harvard University Press, 1993.
Walker, Allan, and Pat Shipman. The Wisdom of the Bones: In Search
of Human Origins. New York: Knopf, 1996.
Homo habilis Homo habilis (“Handy man”) is the scientific
name usually assigned to the earliest species of the
human genus. Louis Leakey (see Leakey, Louis) assigned this
name because this species was the first to make and use stone
tools. The tools, which consisted of little more than stones
from which sharp-edged flakes were struck, are called Oldowan
because they were first found in Olduvai Gorge in Tanzania
(see technology). H. habilis lived in eastern Africa
between about 2.5 million and about 1.5 million years ago.
It is far from clear that the specimens usually assigned to
Homo habilis represent a single species of hominin. Many
anthropologists consider the specimens to represent at least
two species: the larger brained Homo rudolfensis (named after
Lake Rudolf, near which many specimens have been found)
and the smaller brained H. habilis. Some specimens show
variation in characteristics other than brain size. For example,
Olduvai Hominid 62 (OH 62) had relatively longer arms and
shorter legs than other H. habilis, and may therefore represent
yet another, unnamed species. However, the variation
in brain size within H. habilis, broadly defined, is less than
the differences between males and females of some species of
apes, which raises the possibility that H. habilis was a single
species. For convenience, the more inclusive definition of H.
habilis will be used for the remainder of this entry.
It is clear that one of the genetic lineages within H. habilis
was the ancestor of later humans (see Homo erectus;
Homo ergaster; Homo HeiDelbergensis), but anthropologists
do not know which one. Specimens usually assigned
to H. rudolfensis had more modern skull characteristics, but
specimens usually assigned to H. habilis had more modern
dental characteristics. Some populations of H. habilis coex-
Homo habilis
The “ 0 skull” at the Kenya National Museum (KNM-ER 0)
represents one of the earliest specimens of increased brain size in human
evolution. Found by Richard Leakey and associates, this skull housed
a larger brain than most Homo habilis and may represent a different
species. (Courtesy of Kenneth Garrett/National Geographic Society)
isted with the earliest populations of later Homo species, such
as H. ergaster. It is also clear that H. habilis evolved from an
earlier ancestor (see australopithecines), although which
one is also unclear. All of the gracile australopithecines may
have been extinct by the time H. habilis became common,
but the robust australopithecines coexisted with H. habilis.
H. habilis may therefore represent a state of evolution, transitional
between australopithecines and later humans, rather
than a single species.
The evolutionary state of H. habilis differed from that of
the australopithecines in two important respects:
• Brain size. H. habilis represents the first significant, and
somewhat rapid, advancement in brain size over the range
represented by australopithecines and all modern nonhuman
apes. The Kenya National Museum specimen 1813
(KNM-ER 1813), usually assigned to H. habilis, had a cranial
capacity of 32 cubic inches (510 cc), and the KNM-ER
1470 specimen (see figure on page 191), usually assigned
to H. rudolfensis, had a cranial capacity of 47 cubic inches
(750 cc), both significantly exceeding the approximate
value of 22 cubic inches (350 cc) that represents australopithecines
and modern nonhuman apes.
• Stone tools. Australopithecines probably used stick and
stone tools, just as modern monkeys and chimpanzees do.