A mammal belonging to the order Primates (about 195 species), which includes prosimians, monkeys, apes, and humans. Primates probably evolved from insectivorous climbing creatures like tree shrews and have many adaptations for climbing, including five fingers and five toes with opposable first digits (except in the hind feet of humans). They have well-developed hearing and sight, with forward-facing eyes allowing binocular vision, and large brains. The young are usually produced singly and undergo a long period of growth and development to the adult form. Most primates are arboreal, but the great apes and humans are largely terrestrial.