Primate

The order Primates includes prosimians, monkeys, and apes. Primates are well studied, to a large extent because people are primates. (Humans are apes, within the superfamily Hominoidea.) There are some 240 species of primates alive today, ranging across South America, Africa, and Asia. Since nearly all primates are primarily arboreal (they live in trees), their geo­graphic distribution is largely confined to forest or woodland and to warm regions where all of the trees do not lose their leaves and fruits at the same time.

Traditionally primates are divided into two groups: the Prosimians (lemurs of Madagascar and Africa, lorises of Asia, and tarsiers of Asia) and the Anthropoidea (monkeys and apes). Many primatologists prefer to clas­sify them in two main groups: the Strepsirrhini (lemurs and lorises) and Haplorrhini (tarsiers, monkeys, and apes). The difference between the two classificatory systems is the placement of tarsiers, which demonstrate many evolved features relative to the prosimians.

Primates are a generalized group of mammals defined by a series of char­acters variously present in each species. Tendencies in the primates include:

-An emphasis on the sense of sight and a relative deemphasis on the sense of smell; forward-facing eyes that allow good depth perception; and, in the monkeys and apes, there is color vision.

-Grasping hands, with retention of all five digits; nails (not claws) on the ends of digits; sensitive tactile pads on grasping hands, opposable thumbs; and usually grasping feet.

-Large brains for body size; efficient nourishment of the fetus in utero, with usually one infant born at a time, and a prolonged childhood, allowing for more time to learn; longer lives and a great deal of sociality.

-Generalized diets, eating some combination of insects, fruit, and leaves (there are some specialists in each of those categories); baboons and chimpanzees also hunt vertebrates to a small degree, while humans hunt relatively more.

-Varying social and mating habitats. There are multi-male, multifemale groups (baboons); single male multi-female groups (some gorillas, some baboons); and monogamous (gibbons), polyandrous (tamarins and marmosets), polygynous, and promiscuous mating species (chimpanzees). Some are relatively solitary (for example, orangutans). In some cases males immigrate from their natal group and in others, females do.

The relationship between the primates and other orders is not resolved, despite attempts using morphology and comparisons of molecular biology. Molecular and anatomical comparisons have indicated sister groups, which include Chiroptera (bats), Rodentia (rodents), and Lagamopha (rabbits), among others.

The earliest fossils that are undisputed primates are from a warm epoch called the Eocene, found in North America, North Africa, and Asia, but not in South America or Antarctica.

There is special urgency to preserve primates because they inform sci­entists about humans and human evolution. About one-third of primate species are in danger of extinction because of rampant destruction of their forest habitats via logging and the bush-meat trade.

References

Fleagle, John. Primate Adaptations and Evolution, 2nd ed. New York: Academic Press, 1999.

Strier, Karen. Primate Behavioral Ecology. Needham Heights, MA: Allyn & Bacon, 1999.