Olduvai Gorge The conservation area also protects Olduvai Gorge, situated in the plains area. It is considered the seat of humanity after the discovery of the earliest known specimens of modern humans, Homo habilis as well as the early humans, Paranthropus boisei.   The Olduvai Gorge or Oldupai Gorge is a steep-sided ravine in the Great Rift Valley, which stretches along eastern Africa. Olduvai is in the eastern Serengeti Plains in northern Tanzania and is about thirty miles long. It lies in the rain shadow of the Ngorongoro highlands and is the driest part of the region. [13] The gorge is named after the Maasai word for the wild sisal plant, Sansevieria ehrenbergii, commonly called Oldupaai.   It is one of the most important prehistoric sites in the world and research there has been instrumental in furthering understanding of early human evolution. Excavation work there was pioneered by Mary and Louis Leakey in the 1950s and is continued today by their family. Some believe that millions of years ago, the site was that of a large lake, the shores of which were covered with successive 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.