A primate is a diverse order of mammals that includes lemurs, lorises, tarsiers, monkeys, apes, and humans. They arose 85-55 million years ago from small terrestrial mammals that adapted to living in the trees of tropical forests. Primates are divided into two suborders: the strepsirrhines, which include the lemurs, galagos, and lorisids, and the haplorhines, which include the tarsiers and the simians (monkeys, including apes and humans) .

Primates share several anatomic and functional characteristics reflective of their common ancestry. For example, when compared with body weight, the primate brain is larger than that of other terrestrial mammals, and it has a fissure unique to primates (the Calcarine sulcus) that separates the first and second visual areas on each side of the brain. Whereas all other mammals have claws or hooves on their digits, only primates have flat nails. Some primates do have claws, but even among these there is a flat nail on the big toe (hallux) . In all primates except humans, the hallux diverges from the other toes and together with them forms a pincer capable of grasping objects such as branches.

Primates are among the most social of animals, forming pairs or family groups, uni-male harems, and multi-male/multi-female groups. Non-human primates have at least four types of social systems, many defined by the amount of movement by adolescent females between groups. Primate teeth are distinguishable from those of other mammals by the low, rounded form of the molar and premolar cusps, which contrast with the high, pointed cusps or elaborate ridges of other placental mammals.

The biological order “Primates” is divided into four classifications: Great Apes (bonobos, chimpanzees, gorillas, humans, and orangutans), Small Apes (gibbons), Monkeys, and Prosimians (angwantibos, galagos or bushbabies, lemurs, lorises, pottos, and, somewhat controversially, tarsiers) . There are an estimated 522 primate species, plus an additional estimated 182 subspecies, with astounding diversity.