Chimpanzee

Chimpanzee, often shortened to chimp, is the common name for the two extant species in the genus Pan. The better known chimpanzee is Pan troglodytes, the Common Chimpanzee, living primarily in West, and Central Africa. Its cousin, the Bonobo or "Pygmy Chimpanzee" as it is known archaically, Pan paniscus, is found in the forests of the Democratic Republic of the Congo. The Congo River forms the boundary between the two species.

Most adherents to the theory of evolution hold the view that chimpanzees and humans share a close common ancestor, due to their similar natures and physiology. However, there are millions of species that are similar, due to the fact that they share a common habitat and must have similar structures and physiology in order to survive.

Measurements

A full grown adult male chimpanzee can weigh from 35-70 kilograms (75-155 pounds) and stand 0.9-1.2 meters (3-4 feet) tall, while females usually weigh 26-50 kg (57-110 pounds) and stand 0.66-1 meters (2.0-3.5 feet) tall.

Lifespan

Chimpanzees rarely live past the age of 40 in the wild, but have been known to reach the age of 60 in captivity, and Tarzan star Cheeta is still alive as of 2006 at the age of 74.

Chimpanzee differences

Anatomical differences between Common and Pygmy Chimpanzees are slight, but in sexual and social behavior there are marked differences. Common Chimpanzees have an omnivorous diet, a troop hunting culture based on beta males led by an alpha male, and highly complex social relationships; Bonobos, on the other hand, have a mostly herbivorous diet and an egalitarian, matriarchal, sexually receptive behavior. The exposed skin of the face, hands and feet varies from pink to very dark in both species, but is generally lighter in younger individuals, darkening as maturity is reached. Bonobos have longer arms and tend to walk upright more often than the Common Chimpanzee.^{[Citation Needed]}

Taxonomic relationships

The genus Pan is now considered to be part of the subfamily Homininae to which humans also belong. Evolutionary biologists believe that the two species of chimpanzees are the closest living evolutionary relatives to humans. It is thought that humans shared a common ancestor with chimpanzees and gorillas as recently as four to seven million years ago. Groundbreaking research by Mary-Claire King in 1973 found 99% identical DNA between human beings and chimpanzees, although research since has modified that finding to about 94% commonality, with at least some of the difference occurring in 'junk' DNA. It has even been proposed that troglodytes and paniscus belong with sapiens in the genus Homo, rather than in Pan. One argument for this is that other species have been reclassified to belong to the same genus on the basis of less genetic similarity than that between humans and chimpanzees. Indeed cladistic taxonomy, based on both genetic difference and date of likely divergence, is very clear in placing both extant species of Pan in the genus Homo, mainly because the genus Homo takes precedence on account of being coined first. It is very important, however, to consider where the differences in the genome appear.

A study published by Clark and Nielsen of Cornell University in the December 2003 issue of the journal Science highlights differences related to one of humankind's defining qualities — the ability to understand language and to communicate through speech. These macro-phenotypic differences, however, may owe less to physiology than might be assumed given that Homo sapiens developed modern cultural features long after the modern physiological features were in place and indeed competed averagely against other species of Homo with regard to tools, etc for many millennia. Differences also exist in the genes for smell, in genes that regulate the metabolism of amino acids and in genes that may affect the ability to digest various proteins.

Fossils

Many human fossils have been found, but chimpanzee fossils were not described until 2005. Existing chimpanzee populations in West and Central Africa do not overlap with the major human fossil sites in East Africa. However, chimpanzee fossils have now been reported from Kenya. The evolutionist researchers who discovered them asserted: "These fossils, from the Kapthurin Formation, Kenya, show that representatives of Pan were present in the East African Rift Valley during the Middle Pleistocene, where they were contemporary with an extinct species of Homo.".