The Olduvai Gorge or Oldupai Gorge in Tanzania is one of the most important paleoanthropological sites in the world; it has proven invaluable in furthering understanding of early human evolution. A steep-sided ravine in the Great Rift Valley that stretches across East Africa, it is about 48 km (30 mi) long, and is located in the eastern Serengeti Plains in the Arusha Region about 45 kilometres (28 miles) from Laetoli, another important archaeological site of early human occupation. The British/Kenyan paleoanthropologist-archeologist team Mary and Louis Leakey established and developed the excavation and research programs at Olduvai Gorge which achieved great advances of human knowledge and world-renowned status.
Homo habilis, probably the first early human species, occupied Olduvai Gorge approximately 1.9 million years ago (mya); then came a contemporary australopithecine, Paranthropus boisei, 1.8 mya, followed by Homo erectus, 1.2 mya. Our species Homo sapiens, which is estimated to have emerged roughly 300,000 years ago, is dated to have occupied the site 17,000 years ago.
The site is significant in showing the increasing developmental and social complexities in the earliest humans, or hominins, largely revealed in the production and use of stone tools. Prior to tools, evidence of scavenging and hunting can be noted—highlighted by the presence of gnaw marks that predate cut marks—and of the ratio of meat versus plant material in the early hominin diet. The collecting of tools and animal remains in a centralized area is evidence of developing social interaction and communal activity. All these factors indicate an increase in cognitive capacities at the beginning of the period of hominids transitioning to hominin—that is, to human—form and behavior.