chimpanzees, gorillas, orangutans, humans
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.
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. |
