A Tanzanian gorge pushed human origins back a million years

Louis and Mary Leakey spent decades excavating Olduvai Gorge before their 1959 discovery of 'Zinjanthropus' and, soon after, fossils of Homo habilis -- a species that used stone tools nearly two million years ago. The finds shifted the accepted birthplace of humanity to East Africa and set the template for modern paleoanthropology fieldwork.