On July 17, 1959, Mary Leakey left her camp and went out to search the layers of sediment in Olduvai Gorge in Tanzania, as she and her husband Louis Leakey had done for almost 30 years. Their primary goal was to find fossils of our human relatives (hominins), and as hot, dusty, backbreaking, painstakingly slow and what many friends and fellow scientists might call impossible as that goal seemed, they were determined to reach it.