Until recently, most classifications included only humans in this family; other apes were put in the family Pongidae (from which the gibbons were sometimes separated as the Hylobatidae). The evidence linking humans to gorillas and chimps has grown dramatically in the past two decades, especially with increased use of molecular techniques. It now appears that chimps, gorillas, and humans form a clade of closely related species; orangutans are slightly less close phylogenetically, and gibbons are a more distant branch. Here we follow a classification reflecting those relationships. Chimps, gorillas, humans, and orangutans make up the family Hominidae; gibbons are separated as the closely related Hylobatidae. Thus constituted, the Hominidae includes 4 genera and 5 species. Its nonhuman members are restricted to equatorial Africa, Sumatra and Borneo. Hominid fossils date to the Miocene and are known from Africa and Asia.
chimpanzees, gorillas, orangutans, humans
Hominids range in weight from 48 kg to 270 kg. Males are larger than females. Hominids are the largest primates, with robust bodies and well-developed forearms. Their pollex and hallux are opposable except in humans, who have lost opposability of the big toe. All digits have flattened nails. No hominid has a tail, and none has ischial callosities. Numerous skeletal differences between hominids and other primates are related to their upright or semi-upright stance.
All members of this family have large braincase. Most have a prominent face and prognathous jaw; again, humans are exceptional. All are catarrhine, with nostrils close together and facing forward and downward. The dental formula is the same for all members of the group: 2/2, 1/1, 2/2, 3/3 = 32. Hominids have broad incisors and their canines are never developed into tusks. The upper molars are quadrate and bunodont; the lowers are bunodont and possess a hypoconulid. The uppers lack lophs connecting labial and lingual cusps and thus, in contrast to cercopithecids, are not bilophodont.
Hominids are omnivorous, primarily frugivorous or folivorous. All but humans are good climbers, but only the orangutan is really arboreal.
Members of this family are well-known for the complexity of their social behavior. Facial expression and complex vocalizations play an important role in the behavior of hominids. All make and use nests. Hominids generally give birth to a single young, and the period of parental care is extended.
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