It has four confirmed subspecies and a fifth proposed subspecies. The chimpanzee and the closely related bonobo (sometimes called the "pygmy chimpanzee") are classified in the genus Pan. Evidence from fossils and DNA sequencing shows that Pan is a sister taxon to the human lineage and are humans' closest living relatives.
The chimpanzee is covered in coarse black hair, but has a bare face, fingers, toes, palms of the hands, and soles of the feet. It is larger and more robust than the bonobo, weighing 40–60 kg (88–132 lb) for males and 27–50 kg (60–110 lb) for females and standing 100 to 170 cm (3.3 to 5.6 ft). Its gestation period is eight months. The infant is weaned at about three years old, but usually maintains a close relationship with its mother for several years more. It lives in groups which range in size from 15 to 150 members, although individuals travel and forage in much smaller groups during the day. The species lives in a strict male-dominated hierarchy, where disputes are generally settled without the need for violence. Nearly all chimpanzee populations have been recorded using tools, modifying sticks, rocks, grass and leaves and using them for acquiring honey, termites, ants, nuts and water. The species has also been found creating sharpened sticks to spear small mammals.
The chimpanzee is listed on the IUCN Red List as an endangered species. Between 170,000 and 300,000 individuals are estimated across its range. The biggest threats to the chimpanzee are habitat loss, poaching and disease. Chimpanzees appear in Western popular culture as stereotyped clown-figures, and have featured in entertainments such as chimpanzees' tea parties, circus acts and stage shows. They are sometimes kept as pets, though their strength and aggressiveness makes them dangerous in this role. Some hundreds have been kept in laboratories for research, especially in America. Many attempts have been made to teach languages such as American Sign Language to chimpanzees, with limited success; for example, sentences do not grow in length with more training.