The genus Pan consists of two extant species: the bonobo and the chimpanzee. Taxonomically, these two ape species are collectively termed panins; however, both species are more commonly referred to collectively using the generalized term chimpanzees, or chimps. Together with humans, gorillas, and orangutans, they are part of the family Hominidae (the great apes, or hominids). Native to sub-Saharan Africa, chimpanzees and bonobos are currently both found in the Congo jungle, while only the chimpanzee is also found further north in West Africa. Both species are listed as endangered on the IUCN Red List of Threatened Species, and in 2017 the Convention on Migratory Species selected the chimpanzee for special protection.
Chimpanzee and bonobo: comparison The chimpanzee (P. troglodytes), which lives north of the Congo River, and the bonobo (P. paniscus), which lives south of it, were once considered to be the same species, but since 1928 they have been recognized as distinct. In addition, P. troglodytes is divided into four subspecies, while P. paniscus is undivided. Based on genome sequencing, these two extant Pan species diverged around one million years ago.
The most obvious differences are that chimpanzees are somewhat larger, more aggressive and male-dominated, while the bonobos are more gracile, peaceful, and female-dominated. Their hair is typically black or brown. Males and females differ in size and appearance. Both chimpanzees and bonobos are some of the most social great apes, with social bonds occurring throughout large communities. Fruit is the most important component of a chimpanzee's diet; but they will also eat vegetation, bark, honey, insects and even other chimpanzees or monkeys. They can live over 30 years in both the wild and captivity.
Chimpanzees and bonobos are equally humanity's closest living relatives. They use a variety of sophisticated tools and construct elaborate sleeping nests each night from branches and foliage. Their learning abilities have been extensively studied. There may even be distinctive cultures within populations. Field studies of Pan troglodytes were pioneered by primatologist Jane Goodall.
Names The genus name Pan was first introduced by Lorenz Oken in 1816. While Oken did not give a rationale for his choice, it is generally thought to have been inspired by the name of the Greek god Pan. An alternative Theranthropus was suggested by Brookes 1828 and Chimpansee by Voigt 1831. Troglodytes was not available, as it had been given as the name of a genus of wren in 1809, for "cave-dweller", reflecting the tendency of some wrens to forage in dark crevices. The International Commission on Zoological Nomenclature adopted Pan as the only official name of the genus in 1895, though the "cave-dweller" connection was able to be included, albeit at the species level (Pan troglodytes – the common chimpanzee) for one of the two species of Pan.
The first use of the name "chimpanze" is recorded in The London Magazine in 1738,The London Magazine 465, September 1738. "A most surprising creature is brought over in the Speaker, just arrived from Carolina, that was taken in a wood at Guinea. She is the Female of the Creature which the Angolans call chimpanze, or the mockman." (cited after OED) glossed as meaning "mockman" in a language of "the Angolans" (apparently from a Bantu language; reportedly modern Vili (Civili), a Zone H Bantu language, has the comparable ci-mpenzi). The spelling chimpanzee is found in a 1758 supplement to Chamber's Cyclopædia."Chimpanzee, the name of an Angolan animal […] In the year 1738, we had one of these creatures brought over into England." (cited after OED) The colloquialism "chimp" was most likely coined some time in the late 1870s.
The chimpanzee was named Simia troglodytes by Johann Friedrich Blumenbach in 1776. The species name troglodytes is a reference to the Troglodytae (literally "cave-goers"), an African people described by Greco-Roman geographers. Blumenbach first used it in his De generis humani varietate nativa liber ("On the natural varieties of the human genus") in 1776, Linnaeus 1758 had already used Homo troglodytes for a hypothetical mixture of human and orangutan. BHL BioStor corrigendum in Bulletin of zoological nomenclature, 45: 304. (1988) Internet Archive BHL
The bonobo, in the past also referred to as the "pygmy chimpanzee", was given the species name of paniscus by Ernst Schwarz (1929), a Greek-style diminutive of the theonym Pan used by Cicero.
Distribution and habitat There are two species of the genus Pan, both previously called simply chimpanzees: Chimpanzees or Pan troglodytes, are found almost exclusively in the heavily forested regions of Central and West Africa. With at least four commonly accepted subspecies, their population and distribution is much more extensive than the bonobos, in the past also called 'pygmy chimpanzee'. Bonobos, Pan paniscus, are found only in Central Africa, south of the Congo River and north of the Kasai River (a tributary of the Congo), in the humid forest of the Democratic Republic of Congo of Central Africa.
Evolutionary history Evolutionary relationship
Phylogeny of superfamily Hominoidea
The genus Pan is part of the subfamily Homininae, to which humans also belong. The lineages of chimpanzees and humans separated in a process of speciation between roughly five to twelve million years ago, making them humanity's closest living relative. Research by Mary-Claire King in 1973 found 99% identical DNA between human beings and chimpanzees. For some time, research modified that finding to about 94% commonality, with some of the difference occurring in noncoding DNA, but more recent knowledge puts the difference in DNA between humans, chimpanzees and bonobos at just about 1%–1.2% again.
Fossils The chimpanzee fossil record has long been absent and thought to have been due to the preservation bias in relation to their environment. However, in 2005, chimpanzee fossils were discovered and described by Sally McBrearty and colleagues. Existing chimpanzee populations in West and Central Africa are separate from the major human fossil sites in East Africa; however, chimpanzee fossils have been reported from Kenya, indicating that both humans and members of the Pan clade were present in the East African Rift Valley during the Middle Pleistocene.
Anatomy and physiology
The chimpanzee's arms are longer than its legs. The male common chimp stands up to high. Male adult wild chimps weigh between 40 and 60 kg with females weighing between 27 and 50 kg. When extended, the common chimp's long arms span one and a half times the body's height. The bonobo is slightly shorter and thinner than the common chimpanzee, but has longer limbs. In trees, both species climb with their long, powerful arms; on the ground, chimpanzees usually knuckle-walk, or walk on all fours, clenching their fists and supporting themselves on the knuckles. Chimpanzees are better suited for walking than orangutans, because the chimp's feet have broader soles and shorter toes. The bonobo has proportionately longer upper limbs and walks upright more often than does the common chimpanzee. Both species can walk upright on two legs when carrying objects with their hands and arms.
The chimpanzee is tailless; its coat is dark; its face, fingers, palms of the hands, and soles of the feet are hairless. 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 and darkens with maturity. A University of Chicago Medical Centre study has found significant genetic differences between chimpanzee populations. A bony shelf over the eyes gives the forehead a receding appearance, and the nose is flat. Although the jaws protrude, a chimp's lips are thrust out only when it pouts.
The brain of a chimpanzee has been measured at a general range of 282–500 cm3. The human brain, in contrast, is about three times larger, with a reported average volume of about 1330 cm3.
Chimpanzees reach puberty between the age of eight and ten years. A chimpanzee's testicles are unusually large for its body size, with a combined weight of about compared to a gorilla's or a human's . This relatively great size is generally attributed to sperm competition due to the polygynandrous nature of chimpanzee mating behaviour. Unlike gorillas, chimpanzees and bonobos have long and filiform penises without a glans.
Longevity In the wild, chimpanzees live to their 30s, while some captured chimps have reached an age of 70 years and older.
Muscle strength
Chimpanzees are known for possessing great amount of muscle strength, especially in their arms. However, compared to humans the amount of strength reported in media and popular science is greatly exaggerated with numbers of four to eight times the muscle strength of a human. These numbers stem from two studies in 1923 and 1926 by a biologist named John Bauman. These studies were refuted in 1943 and an adult male chimpanzee was found to pull about the same weight as an adult man. Corrected for their smaller body sizes, chimpanzees were found to be stronger than humans but not anywhere near four to eight times. In the 1960s these tests were repeated and chimpanzees were found to have twice the strength of a human when it came to pulling weights. The reason chimpanzees are stronger than humans is thought to be that their longer skeletal muscle fibers can generate twice the work output over a wider range of motion compared to those of humans.
Behaviour In the twenty-first century, field researchers have increasingly used camera traps and remote microphones to minimize the impact of direct human observation.
Chimpanzee vs. bonobo
Anatomical differences between the common chimpanzee and the bonobo are slight. Both are omnivorous, adapted to a mainly frugivorous diet. However, sexual and social behaviours differ. Chimpanzees have a troop culture based on beta males led by an alpha male. The bonobo, on the other hand, has more egalitarian, matriarchal, and sexually receptive behaviour. Bonobos frequently have sex, sometimes to help prevent and resolve conflicts. Different groups of chimpanzees also have different cultural behaviour with preferences for types of tools. Chimpanzee aggression tends to be more severe and deadly than bonobo aggression. The average captive chimpanzee sleeps 9 hours and 42 minutes per day.
Contrary to what the scientific name (Pan troglodytes) may suggest, chimpanzees do not typically spend their time in caves, but there have been reports of some of them seeking refuge in caves because of the heat during daytime.
Chimpanzees
Social structure