Chimpanzees

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 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.

Measurements
A full grown adult male chimpanzee can weigh from 35-70 kg (75-155 pounds) and stand 0.9-1.2 m (3-4 ft) tall, while usually females weigh 26-50 kg (57-110 pounds) and stand 0.66-1 m (2-3.5 ft) 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, although 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 behaviour there are marked differences. Common Chimpanzees have an omnivorous diet, a troop hunting culture based on beta males led by a relatively weak alpha, and highly complex social relationships; Bonobos, on the other hand, have a mostly herbivorous diet and an egalitarian, matriarchal, sexually promiscuous culture. 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 much of the time.

History of human interaction
Africans have had contact with chimpanzees for millennia. The first recorded contact of Europeans with chimps took place in present-day Angola during the 1600s. The diary of Portuguese explorer Duarte Pacheco Pereira (1506), preserved in the Portuguese National Archive (Torre do Tombo), is probably the first European document to acknowledge that chimpanzees built their own rudimentary tools.

The first use of the name "chimpanzee", however, did not occur until 1738. The name is derived from a Tshiluba language term "kivili-chimpenze", which is the local name for the animal and translates loosely as "mockman" or possibly just "ape". The colloquialism "chimp" was most likely coined some time in the late 1870s. Science would eventually take the 'pan' occurring in 'chimpanzee' and attribute it to Pan, a rural ancient Greek god of nature. Biologists would apply Pan as the genus name of the animal. Chimps as well as other apes had also been purported to have existed in ancient times, but did so mainly as myths and legends on the edge of Euro-Arabic societal consciousness, mainly through fragmented and sketchy accounts of European adventurers. Apes are mentioned variously by Aristotle, as well as the Bible.

When chimpanzees first began arriving on the European continent, European scientists noted the inaccuracy of these ancient descriptions, which often falsely reported that chimpanzees had horns and hooves. The first of these early trans-continental chimpanzees came from Angola and were presented as a gift to Frederick Henry, Prince of Orange in 1640, and were followed by a few of its brethren over the next several years. Scientists who examined these rare specimens were baffled, and described these first chimpanzees as "pygmies", and noted the animals' distinct similarities to humans. The next two decades would see a number of the creatures imported into Europe, mainly acquired by various zoological gardens as entertainment for visitors.

Darwin's theory of evolution (published in 1859) spurred scientific interest in chimpanzees, as in much of life science, leading eventually to numerous studies of the animals in the wild and captivity. The observers of chimpanzees at the time were mainly interested in behaviour as it related to that of humans. This was less strictly and disinterestedly scientific than it might sound, with much attention being focused on whether or not the animals had traits that could be considered 'good'; the intelligence of chimpanzees was often significantly exaggerated. At one point there was even a scheme drawn up to domesticate chimpanzees in order to have them perform various menial tasks (i.e. factory work). By the end of the 1800s chimpanzees remained very much a mystery to humans, with very little factual scientific information available.

The 20th century saw a new age of scientific research into chimpanzee behaviour. Prior to 1960, almost nothing was known about chimpanzee behavior in their natural habitat. In July of that year, Jane Goodall set out to Tanzania's Gombe forest to live among the chimpanzees. Her discovery of chimpanzees making and using tools was groundbreaking, as it had previously been believed that humans were the only species to do so. The most progressive earlier studies on chimpanzees were spearheaded primarily by Wolfgang Köhler and Robert Yerkes, both of whom were renowned psychologists. Both men and their colleagues established laboratory studies of chimpanzees focused specifically on learning about the intellectual, particularly the problem-solving, abilities of chimpanzees. This typically involved basic, practical tests on laboratory chimpanzees, which required a fairly high intellectual capacity (such as how to solve the problem of reaching an out-of-reach banana). Notably, Yerkes also made extensive observations of chimpanzees in the wild which added tremendously to the scientific understanding of chimpanzees and their behaviour. Yerkes studied chimpanzees until World War II, while Köhler concluded five years of study and published his famous Mentality of Apes in 1925 (which is coincidentally when Yerkes began his analyses), eventually concluding that "chimpanzees manifest intelligent behavior of the general kind familiar in human beings ... a type of behaviour which counts as specifically human" (1925).

Common Chimpanzees have been known to attack humans on occasion. There have been many attacks in Uganda by chimpanzees against human children; the results are usually fatal for the children. These attacks are presumed to be due to chimpanzees being drunk and mistaking human children for the Western Red Colobus, one of their favorite meals. The dangers of careless human interactions with chimpanzees are only aggravated by the fact that many chimpanzees perceive humans as potential rivals, and by the fact that the average chimpanzee has over 5 times the upper-body strength of a human male. As a result virtually any angered chimpanzee can easily overpower and potentially kill even a fully grown man, as shown by the attack and near death of former NASCAR driver Saint James Davis.

Some African tribes hunt Bonobos for bush meat as a cheap source of food. This has led to a serious decline in the Bonobo population.

Taxonomic relationships
The genus Pan is now considered to be part of the subfamily Homininae to which humans also belong. 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, and that they have about 95 to 99.4 percent of their DNA in common with humans, 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 &mdash; the ability to understand language and to communicate through speech, though these macro-phenotypic differences 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. See the history of hominoid taxonomy for more about the history of the classification of chimpanzees. See Human evolutionary genetics for more information on the speciation of humans and great apes.

Fossils
Many human fossils have been found, but chimpanzee fossils had not been 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. This would indicate that both humans and members of the Pan clade were present in the East African Rift Valley during the Middle Pleistocene.