Olduvai Gorge or Oldupai Gorge in Tanzania is one of the most important paleoanthropological sites in the world and has been instrumental in furthering the understanding of early human evolution. This site was occupied by Homo habilis approximately 1.9 million years ago, Paranthropus boisei 1.8 million years ago, and Homo erectus 1.2 million years ago. Homo sapiens is dated to have occupied the site 17,000 years ago. Olduvai Gorge is a steep-sided ravine in the Great Rift Valley that stretches through eastern Africa. It is in the eastern Serengeti Plains in Arusha Region, Tanzania and is about 30 mi long. It is located 28 mi from the Laetoli archaeological site.

This site is significant in showing increased developmental and social complexities in hominins. Evidence of this is shown in the production and use of stone tools, which indicates the increase in cognitive capacities. Evidence also indicates the practices of both scavenging and hunting, which are highlighted by the evidence of gnaw marks predating cut marks, and comparisons on percentages of meat versus plant in the early hominid diet. Furthermore, the collection of tools and animal remains in a central area is evidence of increases in social interaction and communal activity.

Researchers dated Olduvai Gorge using radiometric dating of the embedded artifacts, mostly through potassium-argon dating and argon–argon dating.
German Neurologist Wilhelm Kattwinkel traveled to Olduvai Gorge in 1911, where he noticed many fossil bones of an extinct three-toed horse. Kattwinkel’s discovery inspired Professor Hans Reck to lead a team to Olduvai Gorge in 1913. There, he found a hominid skeleton, but unfortunately the start of World War I halted his research.

In 1931, Louis Leakey found Olduvai fossils in Berlin and thought Olduvai Gorge held information on human origins, and thus began excavating there. Louis and Mary Leakey are the archaeologists responsible for most of the excavations and discoveries of the hominid fossils in Olduvai Gorge. Their finds, when added to the prior work of Raymond Dart and Robert Broom, convinced most Paleoanthropologists that humans originally evolved in Africa. At the Frida Leakey Korongo site, named after Louis’ first wife in 1959, Mary found remains of the robust australopithecine Zinjanthropus boisei (now known as Paranthropus boisei). The specimen’s age of 1.75 million years radically altered the accepted ideas about the time scale of human evolution. They also found and studied more than 2,000 stone tools and flakes at the site, which were classified as Oldowan tools, in addition to an abundance of faunal remains. Louis Leakey’s son Jonathan found the first specimen of Homo habilis, a jaw fragment, at Olduvai in 1960.

The geology of Olduvai Gorge and the surrounding region was studied in detail by Richard L. Hay, who worked at the site between 1961 and 2002. His finding revealed, millions of years ago, the site was a large lake, with shores covered with deposits of volcanic ash. Around 500,000 years ago, seismic activity diverted a nearby stream which began to cut down into the sediments, revealing seven main layers in the walls of the gorge.

The name Olduvai is a misspelling of Oldupai Gorge, which was adopted as the official name in 2005. Oldupai is the Maasai word for the wild sisal plant „Sansevieria ehrenbergii“, which grows in the gorge.