Baboons are primates comprising the genus Papio, one of the 23 genera of Old World monkeys. The common names of the five species of baboons are the hamadryas, the Guinea (also called the western and the red), the olive, the yellow, and the chacma baboons. They are each native to one of five specific areas of Africa, and the hamadryas baboon is also native to part of the Arabian Peninsula. They are among the largest non-hominoid primates. Baboons have existed for at least two million years.