Baboons are primates comprising the genus Papio, one of the 23 genera of Old World monkeys. There are five species of baboons, commonly known as hamadryas baboon, Guinea baboon, olive baboon, yellow baboon and chacma baboon. Each species is native to one of five areas of Africa and the hamadryas baboon is also native to part of the Arabian Peninsula. Baboons are among the largest non-hominoid primates and have existed for at least two million years.Baboons vary in size and weight depending on the species. The smallest, the Kinda Baboon, is 50 cm (20 in) in length and weighs only 14 kg (31 lb), while the largest, the chacma baboon, is up to 120 cm (47 in) in length and weighs 40 kg (88 lb). All baboons have long, dog-like muzzles, heavy, powerful jaws with sharp canine teeth, close-set eyes, thick fur except on their muzzles, short tails, and nerveless, hairless pads of skin on their protruding buttocks called ischial callosities that provide for sitting comfort. Male hamadryas baboons have large white manes.