Olduvai gorge, also known as Oldupai Gorge and The Cradle of Mankind, lies within the Ngorongoro Conservation Area in Tanzania, Africa. It is about 30 miles long. Millions of years ago the gorge was a large lake with shores covered with deposits of volcanic ash. Around 500,000 years ago seismic activity diverted a nearby stream, which cut into the sedimentary rock, revealing the main layers in the walls of the gorge. Dr. Louis Leakey a paleoanthropologist, did extensive work in this gorge. He believed that early man developed in Africa and spent most of his life studying tools, bones and other artifacts from this area.