Phylogenetically, they are more closely related toapes than toNew World monkeys, with the Old World monkeys and apes diverging from a common ancestor between 25 million and 30 million years ago.[3] Thisclade, containing the Old World monkeys and the apes, diverged from a common ancestor with the New World monkeys around 45 to 55 million years ago.[4][need quotation to verify] The individual species of Old World monkey are more closely related to each other than to apes or any other grouping, with a common ancestor around 14 million years ago.[5]
The smallest Old World monkey is thetalapoin, with a head and body 34–37 centimetres (13–15 in) in length, and weighing between 0.7 and 1.3 kilograms (1.5 and 2.9 lb). The largest is the male mandrill, around 70 centimetres (28 in) in length, and weighing up to 50 kilograms (110 lb)[6] Old World monkeys have a variety of facial features; some havesnouts, some are flat-nosed, and many exhibit coloration. Most have tails, but they are notprehensile.
Old World monkeys are native to Africa and Asia today, inhabiting numerous environments: tropicalrain forests,savannas,shrublands, and mountainous terrain. They inhabited much of Europe in the past; today, the only survivors in Europe are theBarbary macaques ofGibraltar. Whether they were native to Gibraltar or were brought by humans is unknown.
Some Old World monkeys arearboreal, such as thecolobus monkeys; others areterrestrial, such as thebaboons. Most are at least partiallyomnivorous, but all prefer plant matter, which forms the bulk of their diets. Most are highly opportunistic, primarily eating fruit, but also consuming almost any food item available, such as flowers, leaves, bulbs andrhizomes, insects, snails, small mammals,[6] and garbage and handouts from humans.
Twosubfamilies are recognized, theCercopithecinae, which are mainly African, but include the diversegenus ofmacaques, which are Asian and North African, and theColobinae, which includes most of the Asian genera, but also the African colobus monkeys.
The distinction between apes andmonkeys is complicated by the traditionalparaphyly ofmonkeys: Apes emerged as a sister group of Old World monkeys in thecatarrhines, which are a sister group of New World monkeys. Therefore,cladistically, apes, catarrhines and related contemporary extinct groups, such asParapithecidae, are monkeys as well, for any consistent definition of "monkey".[7]
"Old World monkey" may also legitimately be taken to be meant to include all the catarrhines, including apes and extinct species such asAegyptopithecus,[8] in which case the apes, Cercopithecoidea andAegyptopithecus as well as (under an even more expanded definition) even thePlatyrrhini[9] emerged within the Old World monkeys. Historically, monkeys from the "Old World" (Afro-Arabia), somehow drifted to the "New World" some 40 million years ago, forming the "New World monkeys" (platyrrhines). Apes would emerge later within the Afro-Arabia group.
Old World monkeys are medium to large in size, and range fromarboreal forms, such as thecolobus monkeys, to fully terrestrial forms, such as the baboons. The smallest is thetalapoin, with a head and body 34–37 cm in length, and weighing between 0.7 and 1.3 kilograms, while the largest is the malemandrill (the females of the species being significantly smaller), at around 70 cm in length, and weighing up to 50 kilograms.[6]
Most Old World monkeys have tails (the family name means "tailed ape"), unlike the tailless apes. The tails of Old World monkeys are notprehensile, unlike those of theNew World monkeys (platyrrhines).
The distinction of catarrhines from platyrrhines depends on the structure of therhinarium, and the distinction of Old World monkeys from apes depends ondentition (the number of teeth is the same in both, but they are shaped differently). In platyrrhines, the nostrils face sideways, while in catarrhines, they face downward. Other distinctions include both a tubular ectotympanic (ear bone), and eight, not twelve, premolars in catarrhines, giving them adental formula of:2.1.2.32.1.2.3
Several Old World monkeys have anatomical oddities. For example, thecolobus monkeys have stubs for thumbs to assist with their arboreal movement, theproboscis monkey has an extraordinary nose, while thesnub-nosed monkeys have almost no nose at all.
Thepenis of the malemandrill is crimson and thescrotum islilac; the face is also brightly colored. The coloration is more pronounced in dominant males.[10]
Most Old World monkeys are at least partiallyomnivorous, but all prefer plant matter, which forms the bulk of their diet.Leaf monkeys are the most vegetarian, subsisting primarily on leaves, and eating only a small number of insects, while the other species are highly opportunistic, primarily eating fruit, but also consuming almost any food items available, such as flowers, leaves, bulbs andrhizomes, insects, snails, and even small vertebrates.[6] TheBarbary macaque's diet consists mostly of leaves and roots, though it will also eat insects and uses cedar trees as a water source.[12]
Gestation in the Old World monkeys lasts between five and seven months. Births are usually single, although, as with humans, twins occur occasionally. The young are born relatively well-developed, and are able to cling onto their mother's fur with their hands from birth. Compared with most other mammals, they take a long time to reach sexual maturity, with four to six years being typical of most species.
In most species, daughters remain with their mothers for life, so that the basic social group among Old World monkeys is amatrilineal troop. Males leave the group on reaching adolescence, and find a new troop to join. In many species, only a single adult male lives with each group, driving off all rivals, but others are more tolerant, establishing hierarchical relationships between dominant and subordinate males. Group sizes are highly variable, even within species, depending on the availability of food and other resources.[6]
^Setchell, Joanna M.; Dixson, Alan F. (2002). "Developmental variables and dominance rank in adolescent male mandrills (Mandrillus sphinx)".American Journal of Primatology.56 (1):9–25.doi:10.1002/ajp.1060.PMID11793410.S2CID25762754.
^Agustí, Jordi; Antón, Mauricio (2002).Mammoths, Sabretooths, and Hominids: 65 Million Years of Evolution in Europe. New York: Columbia University Press. pp. 216–218.ISBN0-231-11640-3.
^Ciani, Andrea Camperio; Martinoli, Loredana; Capiluppi, Claudio; Arahou, Mohamed; Mouna, Mohamed (2001). "Effects of Water Availability and Habitat Quality on Bark-Stripping Behavior in Barbary Macaques".Conservation Biology.15 (1):259–265.Bibcode:2001ConBi..15..259C.doi:10.1111/j.1523-1739.2001.99019.x.S2CID86080812.
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