A monkey is a primate of the Haplorrhini suborder andsimian infraorder, either an Old World monkey or a New World monkey, but excluding apes (including humans). There are about 260 known living species of monkey. Many are arboreal, although there are species that live primarily on the ground, such as baboons. Monkeys are generally considered to be intelligent. Unlike apes, monkeys usually have tails. Tailless monkeys may be called "apes", incorrectly according to modern usage; thus the tailless Barbary macaque is called the "Barbary ape".
The New World monkeys (superfamily Ceboidea) are classified within the parvorder of Platyrrhini, whereas the Old World monkeys (superfamily Cercopithecoidea) form part of the parvorder Catarrhini, which also includes the hominoids (apes, including humans). Thus, as Old World monkeys are more closely related to hominoids than they are to New World monkeys, the monkeys are not a unitary (monophyletic) group.
Historical and modern terminology
According to the Online Etymology Dictionary, the word "monkey" may originate in a German version of the Reynard the Fox fable, published circa 1580. In this version of the fable, a character named Moneke is the son of Martin the Ape.In English, no very clear distinction was originally made between "ape" and "monkey"; thus the 1910 Encyclopædia Britannicaentry for "ape" notes that it is either a synonym for "monkey" or is used to mean a tailless humanlike primate. Such ambiguities persist. Colloquially, the terms "monkeys" and "apes" may still be used interchangeably.Also, a few monkey species have the word "ape" in their common name, such as theBarbary ape.
Later in the first half of the 20th century, the idea developed that there were trends in primate evolution and that the living members of the order could be arranged in a series, leading through "monkeys" and "apes" to humans. Monkeys thus constituted a "grade" on the path to humans and were distinguished from "apes".
Scientific classifications are now more often based on monophyletic groups, that is groups consisting of all the descendants of a common ancestor. The New World monkeys and the Old World monkeys are each monophyletic groups, but their combination is not, since it excludes hominoids (apes and humans). Thus the term "monkey" no longer refers to a recognized scientifictaxon. The smallest accepted taxon which contains all the monkeys is the infraorder Simiiformes, or simians. However this also contains the hominoids (apes and humans), so that monkeys are, in terms of currently recognized taxa, non-hominoid simians.
A group of monkeys may be commonly referred to as a tribe or a troop.
Physical description
Monkeys range in size from the pygmy marmoset, which can be as small as 117 millimetres (4.6 in) with a 172-millimetre (6.8 in) tail and just over 100 grams (3.5 oz) in weight, to the male mandrill, almost 1 metre (3.3 ft) long and weighing up to 36 kilograms (79 lb). Some are arboreal (living in trees) while others live on the savanna; diets differ among the various species but may contain any of the following: fruit, leaves, seeds, nuts, flowers, eggs and small animals (including insects and spiders).
Some characteristics are shared among the groups; most New World monkeys have prehensile tails while Old World monkeys have non-prehensile tails or no visible tail at all. Old World monkeys have trichromaticcolor vision like that of humans, while New World monkeys may be trichromatic, dichromatic, or—as in the owl monkeys and greater galagos—monochromatic. Although both the New and Old World monkeys, like the apes, have forward-facing eyes, the faces of Old World and New World monkeys look very different, though again, each group shares some features such as the types of noses, cheeks and rumps.
Relationship with humans
The many species of monkey have varied relationships with humans. Some are kept as pets, others used as model organisms in laboratories or in space missions. They may be killed inmonkey drives (when they threaten agriculture) or used as service animals for the disabled.
In some areas, some species of monkey are considered agricultural pests, and can cause extensive damage to commercial and subsistence crops.This can have important implications for the conservation of endangered species, which may be subject to persecution. In some instances farmers' perceptions of the damage may exceed the actual damage.Monkeys that have become habituated to human presence in tourist locations may also be considered pests, attacking tourists.
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