Primates Of Africa

Primates are a diverse order of mammals. They are divided into the strepsirrhines, which include the lemurs, galagos, and lorisids, and the haplorhines, which include the tarsiers and the simians (monkeys and apes, the latter including humans). Primates arose 85–55 million years ago first from small terrestrial mammals, 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, a shoulder girdle allowing a large degree of movement in the shoulder joint, and dextrous hands. Primates range in size from Madame Berthe's mouse lemur, which weighs , to the eastern gorilla, weighing over . There are 376–524 species of living primates, depending on which classification is used. New primate species continue to be discovered: over 25 species were described in the 2000s, 36 in the 2010s, and three in the 2020s.

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. Most primates also have opposable thumbs. 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. Primates have slower rates of development than other similarly sized mammals, reach maturity later, and have longer lifespans. Primates are also the most intelligent animals and non-human primates are recorded to use tools. They may communicate using facial and hand gestures, smells and vocalizations.

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.

Etymology

The English name ''primates'' is derived from Old French or French , from a noun use of Latin , from ('prime, first rank'). The name was given by Carl Linnaeus because he thought this the "highest" order of animals. The relationships among the different groups of primates were not clearly understood until relatively recently, so the commonly used terms are somewhat confused. For example, ''ape'' has been used either as an alternative for ''monkey'' or for any tailless, relatively human-like primate.

Sir Wilfrid Le Gros Clark was one of the primatologists who developed the idea of trends in primate evolution and the methodology of arranging the living members of an order into an "ascending series" leading to humans. Commonly used names for groups of primates such as ''prosimians, monkeys, lesser apes'', and ''great apes'' reflect this methodology. According to our current understanding of the evolutionary history of the primates, several of these groups are paraphyletic, or rather they do not include all the descendants of a common ancestor.

In contrast with Clark's methodology, modern classifications typically identify (or name) only those groupings that are monophyletic; that is, such a named group includes ''all'' the descendants of the group's common ancestor.

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

All groups with scientific names are clades, or monophyletic groups, and the sequence of scientific classification reflects the evolutionary history of the related lineages. Groups that are traditionally named are shown on the right; they form an "ascending series" (per Clark, see above), and several groups are paraphyletic:

* Prosimians contain two monophyletic groups (the suborder Strepsirrhini, or lemurs, lorises and allies, as well as the tarsiers of the suborder Haplorhini); it is a paraphyletic grouping because it excludes the Simiiformes, which also are descendants of the common ancestor Primates.
* Monkeys comprise two monophyletic groups, New World monkeys and Old World monkeys, but is paraphyletic because it excludes hominoids, superfamily Hominoidea, also descendants of the common ancestor Simiiformes.
* Apes as a whole, and the great apes, are paraphyletic if the terms are used such that they exclude humans.

Thus, the members of the two sets of groups, and hence names, do not match, which causes problems in relating scientific names to common (usually traditional) names. Consider the superfamily Hominoidea: In terms of the common names on the right, this group consists of apes and humans and there is no single common name for all the members of the group. One remedy is to create a new common name, in this case ''hominoids''. Another possibility is to expand the use of one of the traditional names. For example, in his 2005 book, the vertebrate palaeontologist Benton wrote, "The apes, Hominoidea, today include the gibbons and orangutan ... the gorilla and chimpanzee ... and humans"; thereby Benton was using ''apes'' to mean hominoids. In that case, the group heretofore called ''apes'' must now be identified as the non-human apes.

, there is no consensus as to whether to accept traditional (that is, common), but paraphyletic, names or to use monophyletic names only; or to use 'new' common names or adaptations of old ones. Both competing approaches can be found in biological sources, often in the same work, and sometimes by the same author. Thus, Benton defines ''apes'' to include humans, then he repeatedly uses ''ape-like'' to mean 'like an ape rather than a human'; and when discussing the reaction of others to a new fossil he writes of "claims that '' Orrorin'' ... was an ape rather than a human".

Classification of living primates

A list of the families of the living primates is given below, together with one possible classification into ranks between order and family. Other classifications are also used. For example, an alternative classification of the living Strepsirrhini divides them into two infraorders, Lemuriformes and Lorisiformes.
* Order Primates
** Suborder Strepsirrhini: lemurs, galagos and lorisids
*** Infraorder Lemuriformes
**** Superfamily Lemuroidea
***** Family Cheirogaleidae: dwarf lemurs and mouse-lemurs (41 species)
***** Family Daubentoniidae: aye-aye (1 species)
***** Family Lemuridae: ring-tailed lemur and allies (21 species)
***** Family Lepilemuridae: sportive lemurs (26 species)
***** Family Indriidae: woolly lemurs and allies (19 species)
**** Superfamily Lorisoidea
***** Family Lorisidae: lorisids (16 species)
***** Family Galagidae: galagos (23 species)
** Suborder Haplorhini: tarsiers, monkeys and apes
*** Infraorder Tarsiiformes
**** Family Tarsiidae: tarsiers (14 species)
*** Infraorder Simiiformes (or Anthropoidea)
**** Parvorder Platyrrhini: New World monkeys
***** Family Callitrichidae: marmosets and tamarins (49 species)
***** Family Cebidae: capuchins and squirrel monkeys (29 species)
***** Family Aotidae: night or owl monkeys (douroucoulis) (11 species)
***** Family Pitheciidae: titis, sakis and uakaris (56 species)
***** Family Atelidae: howler, spider, woolly spider and woolly monkeys (26 species)
**** Parvorder Catarrhini
***** Superfamily Cercopithecoidea
****** Family Cercopithecidae: Old World monkeys (165 species)
***** Superfamily Hominoidea
****** Family Hylobatidae: gibbons or "lesser apes" (20 species)
****** Family Hominidae: great apes, including humans (8 species)

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 had 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.

Before Anderson and Jones introduced the classification of Strepsirrhini and Haplorhini in 1984, (followed by McKenna and Bell's 1997 work ''Classification of Mammals: Above the species level''), Primates was divided into two superfamilies: Prosimii and Anthropoidea. Prosimii included all of the prosimians: Strepsirrhini plus the tarsiers. Anthropoidea contained all of the simians.

Phylogeny and genetics

Order Primates is part of the clade Euarchontoglires, which is nested within the clade Eutheria of Class Mammalia. Recent molecular genetic research on primates, colugos, and treeshrews has shown that the two species of colugos are more closely related to primates than to treeshrews, even though treeshrews were at one time considered primates. These three orders make up the clade Euarchonta. The combination of this clade with the clade Glires (composed of Rodentia and Lagomorpha) forms the clade Euarchontoglires. Variously, both Euarchonta and Euarchontoglires are ranked as superorders. Some scientists consider Dermoptera to be a suborder of Primates and use the suborder Euprimates for the "true" primates.

Evolution

The primate lineage is thought to go back at least near the Cretaceous–Paleogene boundary or around 63–74 (mya). The earliest possible primate/proto-primate may be '' Purgatorius'', which dates back to Early Paleocene of North America ~66mya. The oldest known primates from the fossil record date to the Late Paleocene of Africa, c.57 mya ('' Altiatlasius'') or the Paleocene-Eocene transition in the northern continents, c. 55 mya (''Cantius'', '' Donrussellia'', '' Altanius'', '' Plesiadapis'' and ''Teilhardina''). Other studies, including molecular clock studies, have estimated the origin of the primate branch to have been in the mid-Cretaceous period, around 85 mya.

By modern cladistic reckoning, the order Primates is monophyletic. The suborder Strepsirrhini, the " wet-nosed" primates, is generally thought to have split off from the primitive primate line about 63 mya, although earlier dates are also supported. The seven strepsirrhine families are the five related lemur families and the two remaining families that include the lorisids and the galagos. Older classification schemes wrap Lepilemuridae into Lemuridae and Galagidae into Lorisidae, yielding a four-one family distribution instead of five-two as presented here. During the Eocene, most of the northern continents were dominated by two groups, the adapiforms and the omomyids. The former are considered members of Strepsirrhini, but did not have a toothcomb like modern lemurs; recent analysis has demonstrated that ''Darwinius masillae'' fits into this grouping. The latter was closely related to tarsiers, monkeys, and apes. How these two groups relate to extant primates is unclear. Omomyids perished about 30 mya, while adapiforms survived until about 10 mya.

According to genetic studies, the lemurs of Madagascar diverged from the lorisoids approximately 75 mya. These studies, as well as chromosomal and molecular evidence, also show that lemurs are more closely related to each other than to other strepsirrhine primates. However, Madagascar split from Africa 160 mya and from India 90 mya. To account for these facts, a founding lemur population of a few individuals is thought to have reached Madagascar from Africa via a single rafting event between 50 and 80 mya. Other colonization options have been suggested, such as multiple colonizations from Africa and India, but none are supported by the genetic and molecular evidence.

Until recently, the aye-aye has been difficult to place within Strepsirrhini. Theories had been proposed that its family, Daubentoniidae, was either a lemuriform primate (meaning its ancestors split from the lemur line more recently than lemurs and lorises split) or a sister group to all the other strepsirrhines. In 2008, the aye-aye family was confirmed to be most closely related to the other Malagasy lemurs, likely having descended from the same ancestral population that colonized the island.

Suborder Haplorhini, the simple-nosed or "dry-nosed" primates, is composed of two sister clades. Prosimian tarsiers in the family Tarsiidae (monotypic in its own infraorder Tarsiiformes), represent the most basal division, originating about 58 mya. The earliest known haplorhine skeleton, that of 55 MA old tarsier-like ''Archicebus'', was found in central China, supporting an already suspected Asian origin for the group. The infraorder Simiiformes (simian primates, consisting of monkeys and apes) emerged about 40 mya, possibly also in Asia; if so, they dispersed across the Tethys Sea from Asia to Africa soon afterwards. There are two simian clades, both parvorders: Catarrhini, which developed in Africa, consisting of Old World monkeys, humans and the other apes, and Platyrrhini, which developed in South America, consisting of New World monkeys. A third clade, which included the eosimiids, developed in Asia, but became extinct millions of years ago.

As in the case of lemurs, the origin of New World monkeys is unclear. Molecular studies of concatenated nuclear sequences have yielded a widely varying estimated date of divergence between platyrrhines and catarrhines, ranging from 33 to 70 mya, while studies based on mitochondrial sequences produce a narrower range of 35 to 43 mya. The anthropoid primates possibly traversed the Atlantic Ocean from Africa to South America during the Eocene by island hopping, facilitated by Atlantic Ocean ridges and a lowered sea level. Alternatively, a single rafting event may explain this transoceanic colonization. Due to continental drift, the Atlantic Ocean was not nearly as wide at the time as it is today. Research suggests that a small primate could have survived 13 days on a raft of vegetation. Given estimated current and wind speeds, this would have provided enough time to make the voyage between the continents.

Apes and monkeys spread from Africa into Europe and Asia starting in the Miocene. Soon after, the lorises and tarsiers made the same journey. The first hominin fossils were discovered in northern Africa and date back 5–8 mya. Old World monkeys disappeared from Europe about 1.8 mya. Molecular and fossil studies generally show that modern humans originated in Africa 100,000–200,000 years ago.

Although primates are well studied in comparison to other animal groups, several new species have been discovered recently, and genetic tests have revealed previously unrecognised species in known populations. ''Primate Taxonomy'' listed about 350 species of primates in 2001; the author, Colin Groves, increased that number to 376 for his contribution to the third edition of '' Mammal Species of the World'' (MSW3). However, publications since the taxonomy in MSW3 was compiled in 2003 have pushed the number to 522 species, or 708 including subspecies.

Hybrids

Primate hybrids usually arise in captivity, but there have also been examples in the wild. Hybridization occurs where two species' range overlap to form hybrid zones; hybrids may be created by humans when animals are placed in zoos or due to environmental pressures such as predation. 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.

Clones

On 24 January 2018, scientists in China reported in the journal '' Cell'' the creation of two crab-eating macaque clones, named '' Zhong Zhong'' and '' Hua Hua'', using the complex DNA transfer method that produced ''Dolly'' the sheep, for the first time.

Anatomy and physiology

Head

The primate skull has a large, domed cranium