Many Faces of Homo
The Turkana Boy and other discoveries in eastern Africa have given us a fairly detailed account of the genus Homo from 2 to 1.5 million years ago. But until recently, the African record of human evolution around one million years ago was fairly sparse. Today, new finds are beginning to reveal intriguing diversity among the hominids of this time. In Africa, as elsewhere, the emerging story seems to be one of evolutionary experimentation among hominid species, rather than of gradual linear improvement.
Over the course of human evolution, new hominid species continued to emerge and thrive on the African plains. The diverse hominid fossils in this case date to between one and two million years ago and were found at widely dispersed sites, from Eritrea in the north to Lake Turkana in the east to the cave of Swartkrans in South Africa.
Several different species of the genus Homo lived in Africa around two million years ago. Of these species, Homo ergaster is the most plausible ancestor of modern humans--or we could be descended from a species that has yet to be discovered.
Homo ergaster: This species had a body essentially like that of modern humans: long legs, short arms and in some specimens a moderately large brain.
Homo habilis: A hominid with a relatively large brain, this species got its name--which means "handy man"--from its association with stone tools.
Homo rudolfensis: Some researchers do not classify this large-brained hominid as Homo, placing it instead in the genus Kenyanthropus. Little is known about this species.
A Different Look
Found in fragments at the Swartkrans site in South Africa, this skull has a different shape from other fossils discovered in the same area. Researchers originally classified the upper jaw and facial bones as two separate species. In 1977 paleoanthropologist Ron Clarke determined they were from the same individual, perhaps most similar to Homo ergaster.
Featured Fossil: Skull from Olduvai Gorge
This representative of the genus Homo is notable for its large brain, estimated at nearly 80 percent the size of an average modern human brain. But with its heavy construction and bulky ridges above the eyes, this skull is very different from other known Homo skulls found in Africa from the same period.
The oldest stone tools were simple, sharp flakes, but around 1.5 million years ago, a more complex type of tool appeared. For the first time in human history, hominids visualized the tools in their heads before starting to make them. Large, teardrop-shaped hand axes had a well-planned, symmetrical form. They were probably used for a variety of tasks, such as digging for roots, cutting meat and scraping hides.