OH 5 (Olduvai Hominid number 5, also known as Zinjanthropus or "Nutcracker Man"; colloquially as "Dear Boy") is a fossilized cranium and the holotype of the species Paranthropus boisei. It was discovered in Olduvai Gorge, Tanzania, by archaeologist-paleontologist Mary Leakey in 1959.
Her husband and fellow scientist Louis Leakey initially classified the hominid as Zinjanthropus boisei and thought that it was an early ancestor of modern humans that lived approximately 2 million years ago. However, this contention was later withdrawn because of its robust australopithecine features and the discovery of Homo habilis soon thereafter.
Read more about OH 5: Discovery, Analysis, Debate Over Diet