Olduvai Gorge

Olduvai Gorge, a steep-sided ravine cutting through the Serengeti plains of northern Tanzania, has produced one of the most important records of early human evolution and technology anywhere in the world, the result of decades of excavation beginning in the 1930s by Louis and Mary Leakey and continued by their descendants. In 1959, Mary Leakey discovered a robust hominin skull, originally classified as Zinjanthropus boisei (now Paranthropus boisei) and dated to around 1.75 million years old, alongside crude stone tools that gave the "Oldowan" toolmaking tradition — among the earliest known stone tool industries — its name. Subsequent finds at the site span roughly two million years of toolmaking and hominin evolution, including remains attributed to early Homo habilis ("handy man"), named partly for its association with these tools.

Roughly 45 kilometres south of the main gorge, at Laetoli, Mary Leakey's team made a discovery in 1976 that arguably overshadowed even the gorge's own finds: a trail of footprints preserved in volcanic ash, dated to approximately 3.6 million years ago and attributed to Australopithecus afarensis — the same species as the famous "Lucy" skeleton found in Ethiopia. The footprints, made by at least two individuals walking side by side, provided the first direct physical evidence that human ancestors walked fully upright on two legs more than a million years before the genus Homo appeared, settling a long-running debate over whether bipedalism or brain enlargement came first in human evolution — the footprints showed bipedalism came first, in small-brained ancestors not so different in posture, if not in mind, from ourselves.