OH 5, “Zinjanthropus”, “Nutcracker Man”, Australopithecus boisei Discovered by Mary Leakey in 1959 at Olduvai Gorge in Tanzania (Leakey, 1959). Estimated age is 1.8 million years. It is an almost complete cranium; with a brain size is about 530 cc. This was the first specimen of this species. Louis Leakey briefly considered this a human ancestor, but the claim was dropped when Homo habilis was found soon afterwards.