The critical factor that differentiates humans and
apes is bipedal locomotion. Comparative studies of fossils of humans and
animals show differences in the structure of skulls and pelvis. Bipedalism
freed the hands of our ancestors allowing them to carry loads and make tools.
Apart from bipedalism particular aspects of tooth number, size, shape and
enamel of teeth are of value in tracing human ancestry.
The earliest fossil evidence supporting the evolution
of a creature ancestral to humans was found in Kenya. The fossil a single
jawbone has been dated to be 5.5 million years old. More substantial evidence
was found in mid 1990s in northeastern Ethiopia where the remains of more than
40 individuals who lived about 4.4 million years ago were unearthed.
