Chimpanzees (Pan troglodytes) are apes and belong to Hominoidea. Hominoidea includes gibbons and siamangs (Hylobatidae), commonly referred to as the lesser apes, and orangutans (Ponginae), gorillas, chimpanzees, bonobos, and humans (Homininae), often referred to as the great apes (Hartwig, 2002). Apes are anatomically distinct from monkeys in several ways. First, apes typically have longer forelimbs than hindlimbs, the only exception to this trend being humans. Relatively long forelimbs are attributed to the highly suspensory behavior of all non-human apes. In addition to having long forelimbs, apes have a dorsally positioned scapula and globular humeral head. These anatomical features enable apes to have a wide range of overhead movement and aid in suspensory locomotion. Apes also have a broad, short thorax, as opposed to the long, narrow thorax found in monkeys. Finally, unlike all other primates, apes lack a tail (Fleagle, 1999).

Although there are only five extant ape genera, several ape genera have been identified in the fossil record. The first radiation of fossil apes, the proconsulids, occurred in Africa from the late Oligocene to the middle Miocene. Although the best record of proconsulids is found in Africa, specimens have also been found in Asia, suggesting that proconsulids migrated to Asia in the early Miocene (Fleagle 1999). Additionally, fossil apes have been discovered throughout Europe, distributed between the French and Spanish Pyrenees to the Republic of Georgia. The fossil record indicates that African homonoids arrived in Europe during the Miocene between 16 and 17 million years ago, followed by a diversification of apes across Europe and Western Asia (Hartwig, 2002).

The Miocene apes do not have derived morphology that is shared with the African apes and therefore none of the Miocene specimens can be categorized as ancestral to the African ape lineage. Additionally, no fossil specimens from more recent epochs exhibit derived traits that can be linked to the African apes. Therefore, although the last common ancestor between humans and African apes is believed to exist between five and six million years ago, there is no consensus as to what this common ancestor would have looked like (Fleagle, 1999; Hartwig, 2002).

The geographical distribution of chimpanzees ranges across Sub-Saharan Africa from Senegal in the west to Tanzania in the east. In addition to having a wide distribution across the continent, chimpanzees live in diverse habitats. Chimpanzees are most commonly depicted as living in rainforests; however, several populations live in woodlands and dry savannahs where tree are sparse (Fleagle, 1999).

Chimpanzees live in multi-male multi-female groups that are often defined as fission-fusion. In fission-fusion societies, group composition is constantly in flux and is typically dependent upon resource availability. Social groups are based in male philopatry, meaning that males remain in their natal group, while females migrate to new communities (Fleagle, 1999). Chimpanzees exhibit a moderate degree of sexual dimorphism. Males are slightly larger than females with males weighing about 43 kg and females about 34 kg (Smith and Jungers, 1997).

Chimpanzees eat a wide variety of food including, fruits, nuts, leaves, insects, and smaller bodied mammals (Fleagle, 1999). Tool use is well documented among chimps, typically in food acquisition. Sticks are used to fish out termites from logs or ants from anthills and rocks are used to crush nuts with a hard shell.

Like the other apes, chimpanzees engage in suspensory behavior frequently. However, terrestrial quadrupedialism is used to travel between resource rich localities. Chimpanzees use a unique form of quadrupedialism called knuckle-walking. Instead of contacting the ground with the palm or ventral side of the hand, chimps curl their fingers into a fist and contact the ground with the dorsal side of their proximal phalanges. Gorillas are the only other species that exhibit knuckle-walking (Fleagle, 1999).

Additional Information on the Skull

Click on the thumbnails below for labeled images of the skull in standard anatomical views.

Dorsal view	Lateral view	Ventral view

This specimen is the skull and mandible of an adult chimpanzee. It was made available to The University of Texas High-Resolution X-ray CT Facility for scanning by Dr. John Kappelmen of The University of Texas at Austin. Funding for scanning was provided by a National Science Foundation grant (IIS-9816644) to Dr. Kappelman, and funding for image processing was provided by an NSF Digital Libraries Initiative grant to Dr. Timothy Rowe of The University of Texas at Austin.

This specimen was scanned by Matthew Colbert on 26 March 2002 along the coronal axis for a total of 477 1024x1024 pixel slices. Each slice is 0.5 mm thick, with an interslice spacing of 0.4 mm (for a slice overlap of 0.1 mm) and a field of reconstruction of 182.0 mm.

Literature

Fleagle, J. G. 1999. Primate Adaptation and Evolution. Academic Press, San Diego, C.A. 596 pp.

Hartwig, W. C. 2002. The Primate Fossil Record. Cambridge Univeristy Press, Cambridge, U.K.

Smith, R. J. and W. L. Jungers. 1997. Body mass in comparative primatology. Journal of Human Evolution 32:523-559

Links

Pan troglodytes page on the Animal Diversity Web (University of Michigan Museum of Zoology)

Other primates on the eSkeletons Project webpage (The University of Texas at Austin)

See more images of Pan from Last Refuge Ltd.