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Primate
A primate is a member of the biological order Primates (Latin: "prime, first rank"[1]), the group that contains lemurs, the Aye-aye, lorids, galagos, tarsiers, monkeys, and apes, with the last category including humans.[2] With the exception of humans, which now inhabit every continent on Earth,[3] most primates live in tropical or subtropical regions of the Americas, Africa and Asia.[4] Primates range in size from the 30 g (1 ounce) Pygmy Mouse Lemur to the 200 kg (440 pound) Gorilla. According to fossil evidence, the primitive ancestors of primates may have existed in the late Cretaceous period around 65 mya (million years ago), and the oldest known primate is the Late Paleocene Plesiadapis, c 55?58 mya. Molecular clock studies suggest that the primate branch is even older, originating in the mid-Cretaceous period around 85 mya. The Primates order is informally divided into three main groupings: prosimians, monkeys of the New World, and monkeys and apes of the Old World. The bodies of the prosimians most closely resemble those of the early proto-primates. The best-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, which include the familiar capuchin, howler, and squirrel monkeys, live exclusively in the Americas. With the exception of humans, the Old World monkeys and the rest of the apes inhabit Africa and southern and central Asia, although fossil evidence shows many species existed in Europe as well. Primates are adapted for a tree-dwelling lifestyle. Anatomical adaptations support their reliance on vision, their dominant sensory system, rather than smell, the dominant sensory system in most mammals. Three-color vision has developed in some primates. Most primates also have opposable thumbs and some have prehensile tails. Many species are sexually dimorphic, in that males and females have different physical traits, including body mass, canine tooth size, and coloration. Primates have slower rates of development than other similarly sized mammals, and reach maturity later but have longer lifespans. Locomotion techniques used include, leaping from tree to tree, walking on two or four limbs, knuckle-walking and swinging between branches of trees (known as brachiation). Some species live in solitude, others are monogamous, and others live in groups of up to hundreds of members.
Evolutionary historyThe Primates order lies in a tight clustering of related orders (the Euarchontoglires) within the Eutheria, a subclass of Mammalia. Recent molecular genetic research on primates, colugos, and treeshrews has shown that the two species of colugos are more closely related to the primates than the treeshrews,[5] even though the treeshrews were at one time considered primates.[6] 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.[7] EvolutionIn modern, cladistic reckonings, the Primates order is also a true clade. The suborder Strepsirrhini, the "wet-nosed" primates, is generally believed to have split off from the primitive primate line about 63 mya (million years ago),[8] although an earlier date may be possible.[9] 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.[10] Older classification schemes wrap the Lepilemuridae into the Lemuridae and the Galagidae into the Lorisidae, yielding a three-two family split instead of the four-three split as presented here.[10] Other lineages of lower primates inhabited Earth. During the Eocene, most of the northern continents were dominated by two groups, the adapids and the omomyids.[11] The former is considered a member of Strepsirrhini, but it does not have a toothcomb like modern lemurs. The latter was related closely to tarsiers, monkeys, and apes. Adapids survived until about 10 mya.[12] Omomyids, on the other hand, perished about 20 million years earlier.[11] 
Ring-tailed Lemur, a strepsirrhine primate The suborder Haplorrhini, the "dry-nosed" primates, is composed of two sister clades.[10] The prosimian tarsiers in family Tarsiidae (monotypic in its own infraorder Tarsiiformes), represent the most primitive division at about 58 mya.[13][14] The Simiiformes infraorder emerged about 40 mya,[11] and contains the two clades: the parvorder Platyrrhini that developed in South America and contains New World monkeys is one, and the parvorder Catarrhini that developed in Africa and contains the Old World monkeys, humans and the other apes in the other.[10] A third clade, which included the eosimiids, developed in Asia but went extinct millions of years ago.[15] Apes and monkeys spread from Africa into Europe and Asia. Close behind came lorises and tarsiers, also African castaways. The first hominid fossils were discovered in Northern Africa and date back 5?8 mya.[11] Molecular and fossil studies generally show that modern humans originate in Africa 100?200 Ka (thousand years ago).[16] A few new species are discovered each year, and the evaluation of current populations as distinct species is in flux. Biological anthropologist Colin Groves listed about 350 species of primates in Primate Taxonomy in 2001.[17] The recently published third edition of Mammal Species of the World (MSW3) lists 376 species.[10] But even the latter list falls short of current understanding as its collection cutoff was in 2003, and a number of publications since then have pushed up to 406 species. Notable new species not listed in MSW3 include the Bemaraha Woolly Lemur (Avahi cleesei, named after British actor and lemur enthusiast John Cleese) and the GoldenPalace.com Monkey (whose name was put up for auction).Classification
A 1927 drawing of chimpanzees, a gibbon (top right) and two orangutans (center and bottom center). The chimp in the upper left is brachiating; the orang at the bottom center is knuckle-walking. 
Homo sapiens, a member of the order Primates
In older classifications, the Primates were divided into two superfamilies: Prosimii and Anthropoidea.[21] The Prosimii included all of the prosimians: all of Strepsirrhini plus the tarsiers. The Anthropoidea contained all of the simians. HybridsPrimate hybrids usually arise in captivity,[22] but there have also been examples in the wild.[23][24] Hybridization occurs where two species' territories overlap; these hybrid zones may be created by humans when animals are placed in zoos or may be due to environmental pressures such as predation.[23] Intergeneric hybridizations, hybrids of different genera, have also been found in the wild. Although they belong to genera that have been distinct for several million years, interbreeding still occurs between the Gelada and the Hamadryas Baboon.[25] Distinguishing featuresPrimates have diversified in arboreal habitats and although they have primitive (unspecialized) body plan, retain many characteristics that are adaptations to this environment.[26] They are distinguished by the retention of the collar bone in the pectoral girdle; shoulder joints which allow high degrees of movement in all directions; five digits on the fore and hind limbs with opposable thumbs and big toes; fingernails; sensitive tactile pads on the ends of the digits; a trend towards reduced snout and sense of smell; a reduced number of teeth compared to primitive mammals; a complex visual system with high visual acuity and color vision; a large brain in comparison to body size; enlarged cerebral cortex; two mammary glands; typically one young per pregnancy; a long gestation and developmental period and a trend toward holding the torso upright leading to bipedalism.[26] Primates are frequently highly social, with flexible dominance hierarchies.[27] New World species form monogamous pair bonds, and show substantial paternal care of young, unlike most Old World monkeys.[28] Anatomy, physiology and morphologyPrimates have two forward-facing eyes on the front of the skull; binocular vision allows accurate distance perception, useful for the brachiating ancestors of humans.[26] There is a bony ridge above the eye sockets; this ridge reinforces weaker bones in the face which are put under strain during chewing. Strepsirrhines have a postorbital bar, a bone which runs around the eye socket, to protect their eyes; in contrast, the higher primates, haplorrhines, have evolved fully enclosed sockets.[29] 
Primate skull size and weight comparison 
An 1893 drawing of the hands and feet of primates The primate collar bone is retained as prominent element of the pectoral girdle; this allows the shoulder joint broad mobility.[27] Apes have more mobile shoulder joints and arms due to the dorsal position of the scapula, broad ribcages that are flatter front-to-back, and a shorter, less mobile spine compared to Old World monkeys (with lower vertebrae greatly reduced, resulting in tail loss in some species). Old World monkeys are unlike apes in that most have tails, and unlike the New World monkeys in that their tails are never prehensile. Only the New World Atelidae family have prehensile tails. Primates show a trend towards a reduced snout.[27] Technically, the distinction of Old World monkeys from New World monkeys depends on the structure of the nose, and the distinction of Old World monkeys from apes depends on the arrangement of their teeth.[31] In New World monkeys the nostrils face sideways; in Old World monkeys, they face downwards.[31] There is a considerably varied dental pattern in primates and although some have lost most of their incisors, all retain at least one lower incisor.[31] In most strepsirhines, the lower incisors form a toothcomb which is thought to be used in grooming and possibly foraging.[31] Old World monkeys also have eight premolars, compared with twelve in New World monkeys.[31] The Old World species are divided into apes and monkeys depending on the number of cusps on their molars; apes have five, Old World monkeys have four.[31] The main hominid molar cusp (hypocone) evolved in early primate history, while the cusp of the corresponding primitive lower molar (paraconid) was lost. Prosimians are distinguished by their immobilized upper lips, moist tip to their nose and forward-facing lower front teeth. The evolution of color vision in primates is unique among most eutherian mammals. While the remote vertebrate ancestors of the primates possessed three color vision (trichromacy), the nocturnal, warm-blooded, mammalian ancestors lost one of three cones in the retina at the time of dinosaurs. Fish, reptiles and birds are therefore trichromatic while all mammals, with the exception of some primates and marsupials,[32] are strictly dichromats. Catarrhines are routinely trichromatic,[33] platyrrhines, on the other hand, are trichromatic in a few cases only.[34] Howler monkeys have reinvented routine trichromatism through a recent gene duplication of the red-green opsin gene.[35] Howler monkeys are one of the most specialized leaf-eaters of the New World monkeys, fruits are not a major part of their diet,[36] and the type of leaves they prefer to consume (young, nutritive, and digestible), are detectable only by a red-green signal. Field work exploring the dietary preferences of howler monkeys suggests that routine trichromacy was environmentally selected for.[34] 
Distinct sexual size dimorphism can be seen between the male Hamadryas Baboons (grey) and the female (brown). Sexual dimorphismSexual dimorphism, the variation between individuals of different sex in the same species, is often exhibited in simians; though to a greater degree in Old World species (apes and some monkeys) than New World species. Recent studies involve comparing DNA 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[37][38] and canine tooth size[39][40] along with pelage and skin color.[41] The dimorphism can be attributed to and affected by different factors, including mating system,[42] size,[42] habitat and diet.[43] Comparative analyses have substantiated the sexual selection hypotheses, and have generated a more complete understanding of the relationship between sexual selection, natural selection, and mating systems in primates. Studies are helping to find the relative contribution of the various selective and non-selective mechanisms in sexual dimorphism evolution and expression.[44] 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 give some insight into the relationship between sexual dimorphism and growth patterns.[45] Some evidence from the fossil record suggests that there was convergent evolution of dimorphism, and some extinct hominids probably exceeded dimorphism of any living primate.[44] Locomotion
Diademed Sifaka, a vertical clinger and leaper, ready to leap to another tree BehaviorSocial systems
Japanese Macaques bathe together in Jigokudani Hot Spring
Other systems are known to occur as well. For example, with howler monkeys both the males and females typically transfer from their natal group upon reaching sexual maturity, resulting in groups in which neither the males or females are typically related.[36] Some prosimians, colobine monkeys and callitrichid monkeys also use this system.[47] 
Chimpanzees are social animals. These social systems are affected by three main ecological factors: distribution of resources, group size and predation.[28] Within a social group there is a balance between cooperation and competition. Cooperation comes in the form of allogrooming; whereby ectoparasites are removed and wounds cleaned, food sharing and collective defense against predators or of a territory. Competition is demonstrated by aggression and may come about through availability of food, sleeping sites or mates. Aggression is often used in establishing social hierarchies.[28] Interspecific associationsSeveral species of primates are known to associate in the wild. Some of these associations have been extensively studied. In the Tai Forest of Africa, several species coordinate anti-predator behavior. These include the Diana Monkey, Campbell's Mona Monkey, Lesser Spot-nosed Monkey, Western Red Colobus, King Colobus and Sooty Mangabey, which coordinate anti-predator alarm calls.[54] Among the predators of these monkeys is the Common Chimpanzee.[55] The Red-tailed Monkey associates with several species, including the Western Red Colobus, the Blue Monkey, Wolf's Mona Monkey, the Mantled Guereza, the Black Crested Mangabey and Allen's Swamp Monkey.[53] Several of these species are also predated on by the Common Chimpanzee.[56] In South America, but not in Central America, squirrel monkeys associate with capuchin monkeys.[57] This may have more to do with foraging benefits to the squirrel monkeys rather than anti-predation benefits.[57] Cognition and communicationLemurs, lorises, tarsiers, and New World monkeys are reliant on olfactory signals for many aspects of social and reproductive behavior.[4] Specialized glands are used to mark territories with pheromones, which are detected by the vomeronasal organ; this process forms a large part of the communication behavior of these primates.[4] In Old World monkeys and apes this ability is mostly vestigial, and regressed as color vision evolved to become the main sensory organ.[58] Primates also use vocalizations, gestures, and facial expressions to convey psychological state.[59] Development through life stagesPrimates have slower rates of development than other mammals.[47] All non-human primate infants are breastfed by their mothers and rely on them for grooming and transportation.[47] In some species, infants are also protected and transported by males in the group, particularly males who may be their father.[47] Other relatives of the infant, such as siblings and aunts, may also participate in its care.[47] Most primate mothers cease ovulation while breastfeeding an infant; once the infant is weaned the mother can reproduce again.[47] This often leads to weaning conflict with the infant, who often resist weaning and attempt to continue breastfeeding.[47] Primates have a longer juvenile period between weaning and sexual maturity than other mammals of similar size.[47] During the juvenile period, primates are more susceptible than adults to predation and starvation; they gain experience in feeding and avoiding predators during this period.[47] They also learn social and fighting skills, often through playing.[47] In addition to reaching maturity later, primates have longer lifespans than other similarly sized mammals.[47] Lifespans are generally longer for female primates than males.[47] Diet and feeding
Leaf eating Mantled Guereza, a species of black-and-white colobus The Gelada is the only primate species that feeds primarily on grass.[60] Tarsiers are the most carnivorous primates, exclusively eating insects, reptiles, amphibians and other live animals.[61] Capuchin monkeys, on the other hand, can exploit many different types of food, including fruit, leaves, flowers, buds, nectar, seeds, insects and other invertebrates, and small vertebrates such as birds, bird eggs, lizards, squirrels and bats.[36] The Common Chimpanzee has a varied diet that includes predation on other primate species, such as the Western Red Colobus monkey.[55][56] Habitat and distribution
Rhesus Macaque in Indian city of Agra Relationship with humans
Capuchin monkeys' manual dexterity is one reason they can assist quadraplegics. Primates can act as vectors for spreading viruses such as Herpesviridae, Poxviridae, measles, ebola, rabies, the Marburg virus and viral hepatitis.[67] Some of these are zoonotic diseases that can also be transmitted to humans, most notably, the potentially fatal Herpes B Virus.[67] They may be killed in monkey drives to protect agriculture.[68] Human activities have often been detrimental to primates, and have threatened numerous primate species with extinction. Role in scientific researchThousands of non-human primates (NHPs) are used around the world in scientific research as animal subjects.[69] Given their close genetic similarity to humans, they are excellent animal models with which to conduct experiments that are relevant to humans.[70] In particular, the brain and eyes of NHPs more closely parallel human anatomy than that of any other group of animals. Common research applications for NHPs include preclinical trials, neuroscience, and ophthalmology studies. Rhesus Macaques are most commonly used; but other Macaques, African green monkeys, chimpanzees, baboons, squirrel monkeys, and marmosets are also common in animal testing facilities, either wild-caught or purpose-bred.[69][71] In 2004 the European Union used around 10,000 animals; in 2005 in Great Britain alone there were 4,652 experiments conducted on 3,115 non-human primates.[72] As of 2004, 3,100 NHPs were living in captivity in the United States, in zoos, circuses, and laboratories; 1,280 of them were being used in experiments.[73] Governments of many nations have strict care requirements of NHPs kept in captivity. In the US, federal guidelines extensively regulate aspects of NHP housing, feeding, enrichment, and breeding.[74] European campaign groups such as the European Coalition to End Animal Experiments are seeking a ban on all NHP use in experiments as part of the European Union's current review of existing law on animal experimentation.[75] Legal statusWithin the order Primates, only humans are recognized as persons and protected in law by the United Nations Universal Declaration of Human Rights.[76] The status of NHPs is a point of debate, particularly from organizations such as the Great Ape Project[73] and activists such as Ignaas Spruit[77] (director of the Pro-Primates organization), which argue for increased legal rights of NHPs. Conservation
Critically Endangered Sumatran Orangutan Primates with a large body size (over 5 kg) have an increased extinction risk due to their increased profitability to poachers compared to smaller primates.[81] They also have a slow life history with an increased sexual maturity age and a longer period between births. Populations therefore have a slower recovery time after the loss of members to poaching or the pet trade.[83] In some African cities estimates suggest that half of all protein consumed in urban areas comes from the bushmeat trade.[84] Endangered primates such as guenons and the Drill are hunted at levels that far exceed sustainable levels.[84] This is due to their large body size, ease of transport and profitability per animal.[84] As farming encroaches on forest habitats, primates feed on the crops, causing the farmers large economic losses.[85] Primate crop raiding gives locals a negative impression of primates, hindering conservation efforts.[86] Madagascar, home to five endemic primate families, has experienced the greatest extinction of the recent past; since human settlement 1,500 years ago, at least eight classes and fifteen species have become extinct due to hunting and habitat destruction.[4] Among the primates wiped out were Archaeoindris (a lemur larger than a silverback gorilla) and the families Palaeopropithecidae and Archaeolemuridae.[4] In Asia, Hinduism, Buddhism, and Islam prohibit eating primate meat; however primates are still hunted for food.[81] Some smaller traditional religions allow the consumption of primate meat.[87][88] The pet trade and traditional medicine also increase demand for illegal hunting.[89][90][91] The expanding Chinese middle class has also increased demand for exotic pets in recent years.[91] The Rhesus Macaque, a model organism, was protected after overtrapping threatened its numbers in the 1960s; the program was so effective that the macaques are now seen as a pest throughout their range.[80] In Central and South America forest fragmentation and hunting are the two main problems for primates. Large tracts of forest are now rare in Central America.[78][92] This increases the amount of forest vulnerable to edge effects such as farmland encroachment, lower levels of humidity and a change in plant life.[93][94] Movement restriction results in a greater amount of inbreeding, which can cause deleterious effects leading to a population bottleneck, whereby 50% of the population is lost.[95][96] In the United States the main threat is the pet trade. Although primate import for the pet trade was banned in 1975, smuggling still occurs along the United States?Mexico border.[97] Prices range from $3000 for monkeys to $30,000 for apes.[97]There are 21 critically endangered primates, 8 of these species have remained on the IUCN's "The World's 25 Most Endangered Primates" list since the year 2000: the Silky Sifaka, Delacour's Langur, the White-headed Langur, the Gray-shanked Douc, the Tonkin Snub-nosed Langur, the Hainan Black Crested Gibbon, the Cross River Gorilla and the Sumatran Orangutan.[98] Miss Waldron's Red Colobus was recently declared extinct when a report from 1993?1999 could find no trace of the subspecies.[99] However, hunters have killed individuals since then but its prospects remain bleak.[100] See alsoReferencesExternal links
ar:??????? zh-min-nan:Lêng-tióng-l?i bs:Primat (biologija) bg:??????? ca:Primat cs:Primáti da:Primater de:Primaten et:Esikloomalised el:?????????? ????????? es:Primates eo:Primatoj eu:Primate fa:???????? fr:Primates gl:Primate ko:??? hr:Primati id:Primata ia:Primate is:Prímatar it:Primates he:??????? ka:????????? la:Primates lv:Prim?ti lb:Primaten lt:Primatai lij:Primates li:Aapechtege hu:F?eml?sök nl:Primaten ja:??? no:Primater nn:Primat nrm:Prînma oc:Primates pl:Naczelne pt:Primatas ro:Primate ru:??????? scn:Primates simple:Primate sk:Primáty sl:Prvaki sr:??????? sh:Primati su:Primata fi:Kädelliset sv:Primater ta:????? th:????????? vi:B? Linh tr??ng tr:Primatlar uk:??????? zh:??? Source: Wikipedia | The above article is available under the GNU FDL. | Edit this article
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