Chimpanzees
Common chimpanzees (Pan troglodytes) are widespread in the forested parts of West, Central, and East Africa. Pygmy chimpanzees, or bonobos (P. paniscus), are restricted to the swampy lowland forests of the Zaire basin. Despite their names, common chimpanzees are no longer common, and pygmy chimpanzees are no smaller than the other species.
Chimpanzees are partly arboreal and partly ground-dwelling. They feed in fruit trees by day, nest in other trees at night, and can move rapidly through treetops. On the ground chimpanzees usually walk on all fours (knuckle walking), since their arms are longer than their legs. Their hands have fully opposable thumbs and, although lacking a precision grip, can manipulate objects dexterously. Chimpanzees make and use a variety of tools: they shape and strip "fishing sticks" from twigs to poke into termite mounds, and they chew the ends of shoots to fashion fly whisks. They also throw sticks and stones as offensive weapons and hunt and kill young monkeys.
These apes live in small nomadic groups of three to six animals (common chimpanzee) or six to 15 animals (pygmy chimpanzee) which make up a larger community (30–80 individuals) that occupies a territory. Adult males cooperate in defending their territory against predators. Chimpanzeesociety consists of fairly promiscuous mixed-sex groups. Female common chimpanzees are sexually receptive for only a brief period in mid-month (estrous), while female pygmy chimpanzees are sexually receptive for most of the month. Ovulating females capable of fertilization have swollen pink hind quarters and copulate with most of the males in the group. Female chimpanzees give birth to a single infant after a gestation period of about eight months.
A chimpanzee (Pan troglodytes). (Photograph by Nigel J. Dennis. Photo Researchers Inc. Reproduced by permission.)Jane Goodall has studied common chimpanzees for almost 30 years in the Gombe Stream National Park of Tanzania. She found that chimpanzee personalities are as variable as those of humans, that chimpanzees form alliances, have friendships, have personal dislikes, and run feuds. Chimpanzees also have a cultural tradition, that is, they pass learned behavior and skills from generation to generation. Chimpanzees have been taught complex sign language (the chimpanzee larynx won't allow speech) through which abstract ideas have been conveyed. These studies show that chimpanzees can develop a large vocabulary and that they can manipulate this vocabulary to frame new thoughts.
Humans share 98.4% of their genes with chimpanzees, so only 1.6% of human DNA is responsible for all the differences between the two species. The DNA of gorillas differs 2.3% from chimpanzees, which means that the closest relatives of chimpanzees are humans, not gorillas. Further studies of these close relatives would undoubtedly help to better understand the origins of human social behavior and human evolution. Despite this special status, both species of chimpanzees are threatened by the destruction of their forest habitat by hunting and by capture for research.
Resources
Books
Diamond, J. M. The Third Chimpanzee: The Evolution and Future of the Human Animal. New York: Harper Collins, 1992.
Goodall, Jane. Through a Window: My Thirty Years With the Chimpanzees of Gombe. Boston: Houghton Mifflin, 1990.
Peterson, Dale, and Jane Goodall. Visions of Caliban: On Chimpanzees and People. Boston: Houghton Mifflin, 1993.
Periodicals
"Chimp, Human Genes much alike, except for Brain." USA Today (February 12, 2002).
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