Ape, primate, closely related to human beings. The small apes, the gibbon and siamang, and the smallest of the great apes, the orangutan, are found in SE Asia; the other great apes, the gorilla and the chimpanzee, are found in Africa. They vary in size from the 3-ft (1.8-m), 15-lb (6.8-kg) gibbon to the 6-ft (1.8-m), 500-lb (227-kg) gorilla. All are forest dwellers and spend at least some time in trees; unlike monkeys, they can swing hand-over-hand. Their brains, similar in structure to the human brain, are capable of fairly advanced reasoning.