Primates arose 74–63 million years ago first from small terrestrial mammals, which adapted for life in tropical forests: many primate characteristics represent adaptations to the challenging environment among tree tops, including large brain sizes, binocular vision, color vision, vocalizations, shoulder girdles allowing a large degree of movement in the upper limbs, and opposable thumbs (in most but not all) that enable better grasping and dexterity.

[5][6] 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.

[11] Order Primates was established by Carl Linnaeus in 1758, in the tenth edition of his book Systema Naturae,[12] for the genera Homo (humans), Simia (other apes and monkeys), Lemur (prosimians) and Vespertilio (bats).

[1][41] Older classification schemes wrap Lepilemuridae into Lemuridae and Galagidae into Lorisidae, yielding a four-one family distribution instead of five-two as presented here.

[47] 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.

[48][49] The earliest known haplorhine skeleton, that of 55 MA old tarsier-like Archicebus, was found in central China,[50] supporting an already suspected Asian origin for the group.

[70] The primary evolutionary trend of primates has been the elaboration of the brain, in particular the neocortex (a part of the cerebral cortex), which is involved with sensory perception, generation of motor commands, spatial reasoning, conscious thought and, in humans, language.

[71] While other mammals rely heavily on their sense of smell, the arboreal life of primates has led to a tactile, visually dominant sensory system,[71] a reduction in the olfactory region of the brain and increasingly complex social behavior.

[73][74] Primates have forward-facing eyes on the front of the skull; binocular vision allows accurate distance perception, useful for the brachiating ancestors of all great apes.

Fish, reptiles and birds are therefore trichromatic or tetrachromatic, while all mammals, with the exception of some primates and marsupials,[94] are dichromats or monochromats (totally color blind).

Cooperative behaviors in many primates species include social grooming (removing skin parasites and cleaning wounds), food sharing, and collective defense against predators or of a territory.

[105] Genetic evidence indicates that humans were predominantly polygynous for most of their existence as a species, but that this began to shift during the Neolithic, when monogamy started becoming widespread concomitantly with the transition from nomadic to sedentary societies.

[132] Tarsiers are the only extant obligate carnivorous primates, exclusively eating insects, crustaceans, small vertebrates and snakes (including venomous species).

[117] The bonobo is an omnivorous frugivore – the majority of its diet is fruit, but it supplements this with leaves, meat from small vertebrates, such as anomalures, flying squirrels and duikers,[136] and invertebrates.

[138][139] Until the development of agriculture approximately 10,000 years ago, Homo sapiens employed a hunter-gatherer method as their sole means of food collection.

This involved combining stationary food sources (such as fruits, grains, tubers, and mushrooms, insect larvae and aquatic mollusks) with wild game, which must be hunted and killed in order to be consumed.

This change in diet may also have altered human biology; with the spread of dairy farming providing a new and rich source of food, leading to the evolution of the ability to digest lactose in some adults.

[71] 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.

[81] Indris and black-and-white ruffed lemurs make distinctive, loud songs and choruses which maintain territories and act as alarm calls.

[152] Male howler monkeys are among the loudest land mammals as their roars can be heard up to 4.8 km (3.0 mi), and relate to intergroup spacing, territorial protection and possibly mate-guarding.

[162] Primates have advanced cognitive abilities: some make tools and use them to acquire food and for social displays;[163][164] some can perform tasks requiring cooperation, influence and rank;[165] they are status conscious, manipulative and capable of deception;[166][167] they can recognise kin and conspecifics;[168][169] and they can learn to use symbols and understand aspects of human language including some relational syntax and concepts of number and numerical sequence.

[170][171][172] Research in primate cognition explores problem solving, memory, social interaction, a theory of mind, and numerical, spatial, and abstract concepts.

Over two years, anthropologist Anne Russon observed orangutans learning to jab sticks at catfish to scare them out of the ponds and in to their waiting hands.

[182] In Thailand and Myanmar, crab-eating macaques use stone tools to open nuts, oysters and other bivalves, and various types of sea snails.

Scientists filmed a large male mandrill at Chester Zoo (UK) stripping down a twig, apparently to make it narrower, and then using the modified stick to scrape dirt from underneath its toenails.

[192] Accounting for 25% to 40% of the fruit-eating animals (by weight) within tropical rainforests, primates play an important ecological role by dispersing seeds of many tree species.

[205] Although NHP import for the pet trade was banned in the U.S. in 1975, smuggling still occurs along the United States – Mexico border, with prices ranging from US$3000 for monkeys to $30,000 for apes.

[223] In Indonesia large areas of lowland forest have been cleared to increase palm oil production, and one analysis of satellite imagery concluded that during 1998 and 1999 there was a loss of 1,000 Sumatran orangutans per year in the Leuser Ecosystem alone.

[205][231][232] The rhesus macaque, a model organism, was protected after excessive trapping threatened its numbers in the 1960s; the program was so effective that they are now viewed as a pest throughout their range.

[220][233] This increases the amount of forest vulnerable to edge effects such as farmland encroachment, lower levels of humidity and a change in plant life.