Primates

A **primate** (from Latin *primat-*, from *primus*: "prime, first rank") is a eutherian mammal constituting the taxonomic order **Primates**. Primates arose 85–55 million years ago first as plesiadapiformes from small terrestrial mammals (Primatomorpha), which adapted to living in the trees of tropical forests: many primate characteristics represent adaptations to life in this challenging environment, including large brains, visual acuity, color vision, altered shoulder girdle, and dexterous hands. Primates range in size from Madame Berthe's mouse lemur, which weighs 30 g (1 oz), to the eastern gorilla, weighing over 200 kg (440 lb). There are 190–448 species of living primates, depending on which classification is used. New primate species continue to be discovered: over 25 species were described in the first decade of the 2000s, and eleven since 2010.

Primates are divided into two distinct suborders (see diagram under History of terminology). The first suborder is called strepsirrhines (from Greek 'wet-nosed'), which contains lemurs, galagos, and lorisids. These primates can be found throughout Africa, Madagascar, India, and Southeast Asia. The colloquial names of species ending in *-nosed* refer to the rhinarium of the primate. The second suborder is called haplorhines, which contains "dry-nosed" primates (from Greek 'simple-nosed') in the tarsier, monkey, and ape clades. The last of these groups includes humans. Simians (the infraorder called Simiiformes from the Greek word simos, meaning 'flat-nosed') refer to monkeys and apes, which can be classified as Old World monkeys and apes under the infraorder of catarrhines (from Latin 'narrow nosed') or as New World monkeys under the infraorder of platyrrhines (from Latin 'flat-nosed'). Forty million years ago, simians from Africa migrated to South America by drifting on debris (presumably), which gave rise to the New World monkeys. The remaining simians (catarrhines) split into apes (Hominoidea) and Old World monkeys (Cercopithecoidea) approximately twenty-five million years ago. Common species that are simians include the (Old World) baboons, macaques, gibbons, and great apes; and the (New World) capuchins, howlers and squirrel monkeys.

Primates have large brains (relative to body size) compared to other mammals, as well as an increased reliance on visual acuity at the expense of the sense of smell, which is the dominant sensory system in most mammals. These features are more developed in monkeys and apes, and noticeably less so in lorises and lemurs. Some primates are trichromats, with three independent channels for conveying color information. Except for apes and humans, primates have tails. Most primates also have opposable thumbs. Many species are sexually dimorphic; differences may include muscle mass, fat distribution, pelvic width, canine tooth size, hair distribution, and coloration. Primates have slower rates of development than other similarly sized mammals, reach maturity later, and have longer lifespans. Depending on the species, adults may live in solitude, in mated pairs, or in groups of up to hundreds of members. Some primates, including gorillas, humans and baboons, are primarily terrestrial rather than arboreal, but all species have adaptations for climbing trees. Arboreal locomotion techniques used include leaping from tree to tree and swinging between branches of trees (brachiation); terrestrial locomotion techniques include walking on two limbs (bipedalism) and modified walking on four limbs (knuckle-walking).

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. Most primate species remain at least partly arboreal: the exceptions are some great apes, baboons, and humans, who left the trees for the ground and now inhabit every continent.

Close interactions between humans and non-human primates (NHPs) can create opportunities for the transmission of zoonotic diseases, especially virus diseases, including herpes, measles, ebola, rabies, and hepatitis. Thousands of non-human primates are used in research around the world because of their psychological and physiological similarity to humans. About 60% of primate species are threatened with extinction. Common threats include deforestation, forest fragmentation, monkey drives, and primate hunting for use in medicines, as pets, and for food. Large-scale tropical forest clearing for agriculture most threatens primates.

## Phylogenetic tree

The cladogram below shows one possible classification sequence of the living primates: groups that use common (traditional) names are shown on the right.

## Skin color and hair type

Dark skin is camouflage in the dark forest. Chimpanzees are born with white skin so their mother can easily find them but develop dark skin by the time they leave the mother.

People with white skin were forced to cut their hair to avoid getting a severe sunburn and over time their hair became long and straight.

People with dark skin were able to shave their heads and over time their hair became kinky.

Lack of body hair is an adaptation to water and allows people to swim much faster than they would otherwise. Asians in particular have very little body hair.

## References

1. ↑ Although the monophyletic relationship between lemurs and lorisoids is widely accepted, their clade name is not. The term "lemuriform" is used here because it derives from one popular taxonomy that clumps the clade of toothcombed primates into one infraorder and the extinct, non-toothcombed adapiforms into another, both within the suborder Strepsirrhini. However, another popular alternative taxonomy places the lorisoids in their own infraorder, Lorisiformes.