Apes

The common chimpanzee (Pan troglodytes) is relatively widespread in the forested parts of West, Central, and East Africa. A closely related species, the pygmy chimpanzee or bonobo (P. paniscus), is restricted to 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 (this is called knuckle walking), since their arms are longer than their legs. Their hands have fully opposable thumbs and, although lacking a precision grip, they can manipulate objects dexterously. Chimpanzees make and use a variety of simple 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 when they hunt and kill monkeys.

Chimpanzees live in small nomadic groups of 3–6 animals (common chimpanzee) or 6–15 animals (pygmy chimpanzee), which make up a larger community of 30–80 individuals that occupy a territory. Adult male chimpanzees cooperate in defending their territory against predators. Chimpanzee society consists of 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 being fertilized have swollen pink hindquarters 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.

Jane Goodall has studied common chimpanzees for almost 30 years in the Gombe Stream National Park of Tanzania. She has 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 will not allow speech), through which abstract ideas have been conveyed to people. These studies show that chimpanzees can develop a large vocabulary and that they can manipulate this vocabulary to frame original thoughts.

Humans share approximately 95% 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 that of chimpanzees, which means that the closest relatives of chimpanzees are humans, and not gorillas. The close relatedness of chimpanzees (and other apes) with humans is a key element of the ethical argument for a higher standard of care, and even granting of legal rights, for these animals in captivity. Further studies of chimpanzees will undoubtedly help us to better understand the origins of the social behavior and evolution of humans. Despite their status as close relatives of humans, both species of chimpanzees are threatened by the destruction of their forest habitat and by hunting and by capture for research. Both species of chimpanzees are considered endangered, and their international trade is closely regulated by CITES.