Sorenson - Ape

Apes belong to the order of Primates, a collection of complex creatures ranging from smaller, little-known prosimians such as aye-ayes, angwantibos, galagos, lemurs and lorises to the engaging and charismatic chimpanzees, orangutans and gorillas, as well as humans. Although not all have all these features, primates are distinguished by relatively large brains, frontally placed eyes with binocular vision and protected by bony sockets, grasping hands and feet with opposable thumbs and large toes, nails rather than claws, small litters and slowly maturing young. Great variation exists in size and many species are sexually dimorphic. Primates are mainly vegetarian, relying on fruit or other plant material, but many also feed on insects; some occasionally prey on larger animals. They occupy various habitats but most are skilled climbers with specially developed locomotion. While smaller prosimians such as tarsiers and lemurs leap through trees and monkeys run along branches, gibbons and orangutans use brachiation, a specialized style of alternating arm swings, to move rapidly from branch to branch. Gorillas, bonobos and chimpanzees move quadrapedally on the palms, fists or knuckles of their hands, while humans habitually walk bipedally. Generally, features such as the anatomical structure of the shoulders that allows brachiation, shortened spine, absence of a tail, a y-5 cusp pattern on the molars and a moredeveloped brain differentiate apes from monkeys, but in popular usage the terms are often interchangeable.

Like other primates apes communicate vocally, by gestures and by scent and have a variety of social systems and behaviours. Most are gregarious, and even species that tend toward more solitary behaviour are more social where food supplies are abundant. Seasonal distribution of food is a major factor in population densities and movement.

Outside captivity, apes are found in Africa and Asia. Gibbons exist throughout Asia, while orangutans, once distributed from China to Malaysia, now live only in lowland rainforests and swamps in Borneo and Sumatra. African apes, too, live in rain-forests but also occupy other habitats and elevations, includingmountains, dry forests and savanna. In all cases their environments are threatened by commercial logging, plantations, mining and human settlement. Even low levels of human forest usage have a severe impact on ape populations and unrestrained exploitation will mean extinction for the apes, along with other animals.

Orangutans are the most solitary apes. Although females contact them when they are ovulating, males seem intolerant of each others presence and, through their calls, space themselves out in overlapping ranges. But some community behaviour has been noted and these animals coordinate their movements in ways that observers do not fully understand. Gibbons live in monogamous pairs, raising offspring together, and negotiate relationships and territory through loud, prolonged calls and songs. African apes are more social. Gorillas live in groups of up to 50 individuals. These groups usually include one or two mature males, several related junior males and several females and their infants. Young females leave the group and join those of males with whom they mate. Bonobos may congregate in groups of up to 120 individuals and chimpanzees also gather in smaller numbers.

Unique patterns of learned behaviour culture have been noted among different groups of the same species in terms of food processing, production and use of tools and grooming. Tool use, once considered a defining human characteristic, has been seen among birds and monkeys but is widespread among apes, who use different tools for different purposes and who pass on their knowledge through generations.

Debates continue about the relationship of living apes to fossil discoveries. Many extinct forms are missing from the fossil record. The earliest primate fossils may date to the Paleocene about 65 million years ago (MYA) and recognizably at least from the early Eocene epoch, about 55 MYA. These are small animals, resembling living prosimians. In the past primate evolution was explained as adaptation to arboreal life, suggesting that this encouraged selection of the above-mentioned features, but the absence of these features in other arboreal animals has led to explanations based on diet. Many primates subsist on fruit and flowers and primates may have evolved to pluck these foods from slender terminal branches.