Primate Totally Explained

Everything about Primates totally explained

A primate is any member of the biological order Primates, the group that contains all the species commonly related to the lemurs, monkeys, and apes, with the last category including humans. Primates are found all over the world. Non-human primates occur mostly in Central and South America, Africa, and South Asia. A few species exist as far north in the Americas as southern Mexico, and as far north in Asia as northern Japan.
   The order Primates was established by Carl Linnaeus in 1758, in the tenth edition of his book Systema Naturae, for the genera Homo (humans), Simia (other apes and monkeys), Lemur (prosimians) and Vespertilio (bats). In the first edition of the same book (1735), he'd used the name Anthropomorpha for Homo, Simia and Bradypus (sloths). In 1839, Henri-Marie Ducrotay de Blainville, following Linnaeus and imitating his nomenclature, established the orders Secundates (including the suborders Chiroptera, Insectivora and Carnivora), Tertiates (or Glires) and Quaternates (including Gravigrada, Pachydermata and Ruminantia), but these new taxa were not accepted.
   The Latin primas means "one of the first, excellent, noble" (nominative plural primates). The English singular primate was derived via back-formation from the Latin inflected form.
   The Primates order is divided informally into three main groupings: prosimians, monkeys of the New World, and monkeys and apes of the Old World. The prosimians are species whose bodies most closely resemble that of the early proto-primates. The most well known of the prosimians, the lemurs, are located on the island of Madagascar and to a lesser extent on the Comoros Islands, isolated from the rest of the world. The New World monkeys include the familiar capuchin, howler, and squirrel monkeys. They live exclusively in the Americas. Discounting humans, the rest of the simians, the Old World monkeys and the apes, inhabit Africa and southern and central Asia, although fossil evidence shows many species existed in Europe as well.
   According to fossil evidence, primitive ancestors of primates already existed in the late Cretaceous. Molecular clock studies suggest that the primate branch is even more ancient (originating at least in the mid-Cretaceous). They are now thought to be most closely related to flying lemurs and, more distantly, to treeshrews. They probably have descended from Plesiadapiformes.

Description

All primates have five fingers (pentadactyly), a generalized dental pattern, and a primitive (unspecialized) body plan. Another distinguishing feature of primates is fingernails. Opposing thumbs are also a characteristic primate feature, but are not limited to this order; opossums, for example, also have opposing thumbs. These thumbs allow some species to use tools to perform some tasks. In primates, the combination of opposing thumbs, short fingernails (rather than claws) and long, inward-closing fingers is a relic of the ancestral practice of gripping branches, and has, in part, allowed some species to develop brachiation as a significant means of transportation. Forward-facing colour binocular vision was also useful for the brachiating ancestors of humans, particularly for finding and collecting food, although recent studies suggest it was more useful in courtship. All primates, even those that lack the features typical of other primates (like lorises), share eye orbit characteristics, such as a postorbital bar, that distinguish them from other taxonomic orders.

Sexual dimorphism

Simians show some degree of sexual dimorphism. Old World species (apes and some monkeys) often exhibit sexual dimorphism, which can also be found to a lesser degree in some New World species. Recent studies have mainly used the technique of comparative analysis to examine both the variation in the expression of the dimorphism among primates and the fundamental causes of sexual dimorphism. Primates usually have dimorphism in body mass and canine tooth size along with pelage and skin colour. The dimorphism in primates has been attributed to many factors:

Mating system - Polygynous species are more sexually dimorphic than monogamous species, such as the New World monkeys. It is also associated with greater male gonadal investment than what is found in closely related monogamous species.

Size - Larger species are more sexually dimorphic than smaller species. These studies have shown that dimorphism is the product of changes in both male and female traits. Ontogenic scaling, where relative extension of a common growth trajectory occurs, may show some insight into the relationship between sexual dimorphism and growth patterns. There is some evidence from the fossil record that suggests that there was convergent evolution of dimorphism, and some extinct hominids probably exceeded dimorphism of any living primate.

Habitat

Primates evolved from arboreal animals and many modern species live mostly in trees and hardly ever come to the ground. Other species are partially terrestrial, such as baboons and the Patas Monkey. Only a few species are fully terrestrial, such as the Gelada and Humans. Primates live in a diverse number of forested habitats, including rain forests, mangrove forests, and mountain forests to altitudes of over 3000 m. Although most species are generally shy of water, a few are fine swimmers and are comfortable in swamps and watery areas, including the Proboscis Monkey, De Brazza's Monkey and Allen's Swamp Monkey, which even developed small webbing between its fingers. Some primates, such as the Rhesus Macaque and the Hanuman Langur, can exploit human-modified environments and even live in cities.

Classification and evolution

Close relations

The Primate order lies in a tight clustering of related orders (the Euarchontoglires) within the Eutheria, a subclass of Mammalia. Recent molecular genetic research on primates, flying lemurs, and treeshrews has shown that the two species of flying lemur (Dermoptera) are more closely related to the primates than the treeshrews of the order Scandentia, even though the treeshrews were at one time considered primates. These three orders make up the Euarchonta clade. This clade combines with the Glires clade (made up of the Rodentia and Lagomorpha) to form the Euarchontoglires clade. Variously, both Euarchonta and Euarchontoglires are ranked as superorders. Also, some scientists consider Dermoptera a suborder of Primates and call the "true" primates the suborder Euprimates (Hoffstetter, 1978) . | label2=Euarchonta | 2= }} }} }} }}

Classification

In older classifications, the Primates were divided into two superfamilies: Prosimii and Anthropoidea. The Prosimii included all of the prosimians: all of Strepsirrhini plus the tarsiers. The Anthropoidea contained all of the simians.
In modern, cladistic reckonings, the Primate order is also a true clade. The suborder Strepsirrhini, the "wet-nosed" primates, split off from the primitive primate line about 63 million years ago (mya). The seven strepsirhine families are the four related lemur families and the three remaining families that include the lorises, the Aye-aye, the galagos, and the pottos. The recently published third edition of Mammal Species of the World (MSW3) lists 376 species. and by all governments, though to varying degrees. Non-human primates are not classified as persons. The status of non-human primates has generated much debate, particularly through the Great Ape Project which argues for the personhood of the non-human members of the family Hominidae. In 1995 Ignaas Spruit, director of Leiden (Netherlands) based Pro-Primates organization, went farther, as he proposed that some rights should be recognized to all non-human primates. In the same way, the American anthropologist Earnest Albert Hooton, enlarging the sense of the famous quote by Terence, used to say "Primas sum: primatum nil a me alienum puto", that's to say: “I am a primate; nothing about primates is outside of my bailiwick”.

Animal testing

Thousands of primates are used every year around the world in scientific experiments because of their psychological and physiological similarity to humans. Chimpanzees, baboons, marmosets, macaques, and green monkeys are most commonly used in these experiments. In the European Union, around 10,000 were used in 2004, with 4,652 experiments conducted on 3,115 non-human primates in the UK alone in 2005. As of 2004, 3,100 non-human primates were living in captivity in the United States, in zoos, circuses, and laboratories, 1,280 of them being used in experiments.

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