What is Olduvai Gorge?

The spectacular landscape of northern Tanzania, where Olduvai Gorge is situated, is the product of both abrupt high-energy processes like volcanism and plate tectonics and the slower low-energy processes of weathering and erosion operating together over millions of years. During this time, climate has varied from arid to semi-arid and the vegetation and animal populations both fluctuated with the availability of water. Feedback between climate and topography is particularly important in regions of high relief like the East African Rift System (EARS). The modern topography in northern Tanzania is the summation of the interaction of geologic, biologic, and hydrologic processes. Over time these processes have sculpted the Earth surface by erosion of high areas and the transport and deposition of this material into low areas.

Olduvai Gorge was created by the erosion of an incised valley draining water from the Ndutu lake into the OlBalBal depression located at the foot of Ngorongoro. It is part of the Serengeti migratory ecosystem. Erosion has carved its way through different geological strata spanning two million years; from the emergence of the genus Homo to the appearance of our species Homo sapiens. The gorge contains one of the richest and best preserved archaeological and paleontological records for the study of human evolution.

The exploratory expeditions to Olduvai undertaken by the Leakeys from 1931 to 1947 had the following goals: establishing a sequence of the evolutionary stages of culture across all beds, surveying the gorge to spot as many sites as possible for future selection for excavation, and obtaining a picture of the geological history of the gorge and its relevance to the climatic history of East Africa. What Leakey referred to as the second stage of research at Olduvai, initiated in the early 1950s, was focused on finding and excavating “living floors” to reconstruct “early man’s” behaviour. Extensive open air excavations were subsequently carried out at BK and SHK in Bed II. In the meantime, survey continued in Bed I, and by 1959, hominin fossils had been discovered at MK and, most spectacularly with the skull of Zinjanthropus (Paranthropus boisei), at FLK.

The discovery of Zinj switched temporarily the Leakey’s attention from the Bed II “living floors” to the Bed I “living floors”, and it yielded significant funding from the Wilkie and Wenner-Gren Foundations and from the National Geographic Society. This marked a crucial moment in East African paleoanthropology. For paleontology, it led to the discovery of some of the most important hominin fossils in decades, among them the first Homo habilis. For archaeology, it enabled the prolonged excavation of several sites during the 1960s and the horizontal exposure of some of the most impressive “living floors”. Still today, some of these sites (e.g., FLK Zinj) remain the most extensive open-air excavations carried out in early Pleistocene archaeology in Africa.

The abundant, well-preserved fossils and artifacts from these Olduvai Bed I sites have constituted the core of debates about early human behavior for the past half century.