Chimpanzees (or chimps) are the species of
the great apes in the genus Pan,
consisting of the common chimpanzee and the bonobo.
Together with gorillas, they are the only great apes that are currently
restricted in their range to Africa. Native to sub-Saharan Africa, both chimpanzees and bonobos are currently found in
the Congo
jungle.
Chimpanzee and bonobo: differences and commonalities
They were once considered to be one species; however,
since 1928, they have been recognized as two distinct species: the common chimpanzee (P.
troglodytes) who live north of the Congo River, and the bonobo (P. paniscus) who live south
of it. In
addition, P.
troglodytesis divided into four subspecies, while P. paniscus has none.
Based on genome
sequencing, the 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 chimps and bonobos are some of the most social
great apes, with social bonds occurring among individuals in large communities.
Fruit is the most important component of a chimpanzee's diet; however, they
will also eat vegetation, bark, honey, insects and even other chimps or
monkeys. They can live over 30 years in both the wild and captivity.
Chimpanzees and bonobos are equally humanity's closest
living relatives. As such, they are among the largest-brained, and most
intelligent of primates; they use a variety of sophisticated tools and
construct elaborate sleeping nests each night from branches and foliage. They
have both been extensively studied for their learning abilities. There may even
be distinctive cultures within populations. Field studies of Pan troglodytes were pioneered by primatologist Jane Goodall. Both Pan species are
considered to be endangered as human activities have caused severe declines in
the populations and ranges of both species. Threats to wild panina populations
include poaching, habitat destruction, and the illegal pet trade. Several conservation
and rehabilitation organisations are dedicated to the survival of Pan species
in the wild.
The first use of the name "chimpanze" is
recorded in The London Magazine in 1738, 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. The colloquialism "chimp" was most
likely coined some time in the late 1870s.
The common chimpanzee was named Simia troglodytes by Johann
Friedrich Blumenbach in 1776. The species
name troglodytesis 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.
The genus name Pan was
first introduced by Lorenz Oken in 1816. An alternative Theranthropus was suggested by Brookes1828 and Chimpansee by Voigt 1831. Troglodytes was not
available, as it had been given as the name of a genus of wren(Troglodytidae) in 1809.
The International
Commission on Zoological Nomenclature adopted Pan as
the only official name of the genus in 1895. The name is a reference
to Pan, the Greek god of nature and wilderness.
The bonobo, in the past also referred to as the
"pygmy chimpanzee", was given the species name of paniscus by Ernst Schwarz(1929), a diminutive of the theonym Pan.
In his book, The Third Chimpanzee, J. Diamond proposes that P. troglodytes and P. paniscus belong
with H. sapiens in the genus Homo, rather than in Pan. He argues that
other species have been reclassified by genus for less genetic similarity than
that between humans and chimpanzees.
There are two species of the genus Pan, both previously called Chimpanzees:
- Common 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 that 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 forests of the Democratic Republic of Congo of Central Africa.
Evolutionary relationship
Further information: History of hominoid taxonomy
The genus Pan is part of the
subfamily Homininae, to which humans also
belong. The lineages of chimpanzees[dubious – discuss]and
humans separated in a drawn-out process of speciation over the period of roughly between twelve and five
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 states the
difference in DNA between humans, chimpanzees and bonobos at
just about 1%–1.2% again.
Fossils
The chimpanzee[dubious – discuss] 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.
The chimpanzee's brain on the left and the human brain on
the right have been scaled to the same size to show the relative proportions of
their parts. These drawings were in a book made in 1904 by Thomas Henry Huxley.
A chimpanzee's arms are longer than its legs. The male
common chimp stands up to 1.2 m (3.9 ft) 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 their body size, with a
combined weight of about 4 oz (110 g) compared to a gorilla's
1 oz (28 g) or a human's 1.5 ounces (43 g). This relatively
great size is generally attributed to sperm competition due to the polyandrous nature of chimpanzee mating behaviour.
Longevity
One study estimates that chimps live
about 33 years for males, 37 years for females, in the wild, 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 chimp 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 for the higher strength
seen in chimpanzees compared to humans are thought to come from longer skeletal
muscle fibers that can generate twice the work output over a wider range of
motion compared to skeletal muscle fibers in humans.
Behaviour
It is suspected that human observers can influence chimpanzee
behaviour. It is suggested that drones, camera traps and remote microphones
should be used rather than human observers.
Anatomical differences between the common chimpanzee and
the bonobo are slight. Both are omnivorous adapted to a mainly frugivorousdiet. Yet sexual and social behaviours are markedly
different. The common chimpanzee has a troop culture based on beta males led by
an alpha male, and highly complex social relationships. The bonobo, on
the other hand, has egalitarian, nonviolent, matriarchal, 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. The common chimpanzee tends to display greater aggression than
does the bonobo. The average captive chimpanzee sleeps 9.7 hours 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.