Chimpanzee

Evolution

Pan fossils, consisting of three teeth, were discovered in Kenya in 2005 and dated to around 500,000 years ago. They were found in the same area as Homo fossils indicating that both humans and members of the Pan clade coexisted in the East African Rift Valley during the Middle Pleistocene. The teeth show greater similarity to that of the modern chimpanzee than the bonobo.^[17]

Evolutionary biologists and paleontologists have attempted to reconstruct the chimpanzee-human last common ancestor (CHLCA). By the end of the 20th century, it was assumed that humans evolved from a chimpanzee-like ancestor. A 2015 study of Ardipithecus, an early human relative dated 4.4 million years ago (mya) and predating Australopithecus, disputed this interpretation. The study concluded that humans, chimpanzees and bonobos evolved from a generalised species that lacked the acquired traits of both genera.^[18] Subsequent studies disputed this, finding that the hand of Ardipithecus was adapted for suspension climbing and the heel for vertical climbing, much like modern African apes.^[19][20] Academic opinion indicates that at least 24 species of hominin have appeared after the divergence of humans from chimpanzees estimated at 10 to 7 million years ago.^[21]

When describing the extinct species Sahelanthropus in 2002 as part of the Ardipithecus group, Brunet and colleagues noted the combination of ancient features not expressed in chimpanzees that would be considered archaic or derived for a species on the human line (the subtribe Hominina). These latter ancient features being bipedal locomotion and reduced canine teeth, which they interpreted as evidence of its position near the CHLCA. For example, in addition to the study of Ardipithecus in studying traits expressed and not expressed in chimpanzees, researchers such as M. Burnet have examined Sahelanthropus, the oldest Hominina, shifting the centre of origin for the clade away from East Africa and CHLCA origins. They also suggested that Sahelanthropus could be a sister taxon to the 5.5-to-4.5-million-year-old Ardipithecus and later Hominina after the separation from the chimpanzee line.^[22]

Chimpanzees and bonobos are estimated to have split from the human lineage 7–10 mya,^[14] and from each other close to 2 mya.^[23] A 2016 genetic study suggests ancient gene flow (introgression) between 200,000 and 550,000 years ago from the bonobo into the ancestors of central and eastern chimpanzees.^[24] Paleoanthropologist Gerhard Roth has noted that after the separation of the chimpanzee-bonobo line from the human-neanderthal line that the rates of growth of brain volume compared to body weight has been markedly different for these two lines, showing much sharper rate of growth for the human line rather than the chimpanzee-bonobo line.^[25]

Subspecies and population status

Four subspecies of the chimpanzee have been recognised,^[26][27] with the possibility of a fifth:^[24][28]

• Central chimpanzee or the tschego (Pan troglodytes troglodytes), found in Cameroon, the Central African Republic, Equatorial Guinea, Gabon, the Republic of the Congo, and the Democratic Republic of the Congo, with about 140,000 individuals existing in the wild.^[29]
• Western chimpanzee (P. troglodytes verus), found in Ivory Coast, Guinea, Liberia, Mali, Sierra Leone, Guinea-Bissau, Senegal, and Ghana with about 52,800 individuals still in existence.^[30][31]
• Nigeria-Cameroon chimpanzee (P. troglodytes ellioti (also known as P. t. vellerosus)),^[26] that live within forested areas across Nigeria and Cameroon, with 6,000–9,000 individuals still in existence.^[32][33]
• Eastern chimpanzee (P. troglodytes schweinfurthii), found in the Central African Republic, South Sudan, the Democratic Republic of the Congo, Uganda, Rwanda, Burundi, Tanzania, and Zambia, with approximately 180,000–256,000 individuals still existing in the wild.^[34]
• Southeastern chimpanzee, P. troglodytes marungensis, in Burundi, Rwanda, Tanzania, and Uganda. Colin Groves argues that this is a subspecies, being different enough from P. t. schweinfurthii,^[28] but it is not recognised by the IUCN.^[2]

A 2013 genetic study which used samples from the four recognised subspecies found that they can be divided into two branches or clades, the Nigeria-Cameroon and Western chimpanzee forming one clade and the Central and Eastern subspecies belonging to the other.^[35] Genetic evidence suggests that chimpanzee populations were interconnected until around 500,000 years ago following climatic changes during the transition from the Pliocene to the Pleistocene.^[36]

Genome

A draft of the chimpanzee genome was first published in 2005 and revealed that almost 99% of the species DNA sequences were shared with humans, and around 30% of proteins perfectly matched.^[37][38] A more complete chimpanzee genome was published in 2025. The paper concluded that while chimpanzee and human autosomal (non-sex) DNA differ by only 1.5% to 1.6% in one-to-one genetic code sequences, when accounting for insertions, deletions and non-coding material, a 12.5% to 13.3% difference was found. The X chromosomes were more similar while the Y chromosomes were more divergent.^[39] The two species differ in the number of chromosome pairs, with chimpanzees having 24 and humans 23; this is due to a fusion in two chromosomes during human evolution, producing human chromosome 2.^[40] A 2006 study concluded that around 6% of the gene inventory in chimpanzees and humans differ due to gene duplications and deletions, contributing to major genetic differences between the two species.^[41] In addition, a 2012 study comparing brain tissue found that chimpanzees and humans diverged significantly in the de-activating of genes.^[42]

Diet

The chimpanzee primarily eats fruit, but also consumes leaves, seeds, blossoms, stems, pith, bark, and resin.^[72][73] A study in Budongo Forest, Uganda found that chimpanzees concentrate the majority of their feeding time (64.5%) on fruits (84.6% of which being ripe), particularly those from two species of Ficus, Maesopsis eminii, and Celtis gomphophylla. In addition, 19% of feeding time was spent on arboreal leaves, mostly Broussonetia papyrifera and Celtis mildbraedii.^[74] The consumption of woody material like bark appears to have a supplemental or medicinal function rather than just being an alternative food source during scarcity.^[75] In savanna habitats, chimpanzees have adapted to eating seeds and unripe fruits.^[76] While the chimpanzee is mostly herbivorous, it does eat honey, soil, insects, birds and their eggs, and small to medium-sized mammals, including other primates.^[77][78] Insect species consumed include the weaver ant species Oecophylla longinoda, termites of the genus Macrotermes, and honey bees.^[66][67]

When in large groups, chimpanzees can prey on mammals which include monkeys like the Western red colobus, the king colobus and baboons, non-simian primates like galagos, rodents like squirrels and hooved mammals like bushpigs, blue duikers, sunis and bushbuck fawns.^[79][80] The red colobus is the most common prey,^[81] though Jane Goodall documented many occasions within Gombe Stream National Park of chimpanzees and western red colobus monkeys ignoring each other despite close proximity.^[63] Meat makes up a small portion of their diet, and does not appear to be a high-quality food source since females—who need the energy they can get when pregnant and nursing young—eat far less of it than males. Nevertheless, it is suggested to have some importance in providing nutrients that help in brain development. Chimpanzees are more likely to hunt when fruit is more abundant, since more individuals aggregate during this time and hunting requires large groups.^[82]

Mortality and health

A 2017 study of the Ngogo community in Kibale National Park found that, when environmental conditions are favourable, chimpanzees have an average life expectancy of nearly 33 years, which is within the expectancy of human hunter gatherers (27–37 years). By contrast, the Kanyawara chimpanzees, which also live in Kibale, have an average life expectancy of 20 years. The life expectancy of chimpanzees at Gombe and Taï average 18 and 13 years respectively.^[83] Captive chimpanzees have been recorded to live over 60 years and wild ones can possibly live as long.^[83][84] One study of the Kasekela chimpanzee community in Gombe estimated that around 58% of deaths (with known causes) were due to disease, while around 20% were caused by other chimpanzees.^[85]

Leopards prey on chimpanzees in some areas.^[86][87] It is possible that some mortality caused by leopards can be attributed to individuals that have specialised in killing chimpanzees.^[86] Chimpanzees may react to a leopard's presence with loud vocalising, vegetation shaking, throwing objects and climbing up trees.^[86][88] The apes have been recorded confronting and harassing leopards, stealing their kills and even killing cubs.^[89][90] At least four chimpanzee may fallen prey to lions at Mahale Mountains National Park and the larger group sizes of savanna chimpanzees may have developed as a response to threats from these big cats. Chimpanzees are recorded to react to lions by retreating up trees, shaking branches, vocalising or even silence.^[91]

Less than half the parasite and microbe species that infest chimpanzees also infest humans, however, humans show much more overlap with omnivorous, savanna-dwelling baboons. The chimpanzee is host to the louse species Pediculus schaeffi, a close relative of P. humanus, which lives in human head and body hair. By contrast, the human pubic louse Pthirus pubis is closely related to Pthirus gorillae, which infests gorillas.^[92] The mite species Sarcoptes scabiei may infest chimpanzees and cause mange.^[85] A 2023 study of chimpanzees in Kibale identified seven species of ticks as parasites, the most numerous being the species Haemaphysalis parmata.^[93] A 2017 study of gastrointestinal parasites of wild chimpanzees in degraded forest in Uganda found nine species of protozoa, five nematodes, one cestode, and one trematode. The most prevalent species was the protozoan Troglodytella abrassarti.^[94] The bacteria species Streptococcus pneumoniae and S. pyogenes cause a respiratory diseases in chimpanzees, which are recorded to be the most common cause of disease related deaths in the Kasekela community.^[85] A study found that chimpanzee nests contain fewer skin bacteria and external parasites, but higher microbial diversity from the surrounding environment, compared to human beds.^[95]

Group structure

Chimpanzees live in communities within home ranges which average 4 km (2.5 mi) in diameter. Communities typically consist of as many as 200 members,^[98] though the apes spend most of their time traveling in small, temporary groups consisting of six or less individuals. These groups may consist of any combination of age and sexes. Both males and females sometimes travel alone.^[63] Chimpanzee communities are considered fission–fusion societies, as groups consistently split off and merge based upon varying factors.^[99] At the core these social structures are males, who remain in their natal communities, while females generally emigrate at adolescence. Males in a community are more thus likely to be related to one another than females are to each other, and males are generally dominant over females.^[100][101] Males and sexually receptive females are the most social members of a community. Males appear to be social with individuals of any sex or class, while receptive females typically avoid each other and non-receptive females prefer to associate amongst themseleves.^[102]

Male chimpanzees compete aggressively and exist in a linear dominance hierarchy. Top-ranking males tend to be aggressive even when there is dominance stability in the hierarchy.^[103] This is probably due to the chimpanzee's fission-fusion society, with male chimpanzees leaving groups and returning after extended periods of time. With this, a dominant male is unsure if any changes have occurred in his absence and must re-establish his dominance. Thus, a large amount of aggression occurs within five to fifteen minutes after a reunion. During these encounters, displays of low level aggression are generally preferred over physical attacks of high aggression.^[103][104] Males maintain and improve their social ranks by forming coalitions, which have been characterised as "exploitative" and based on an individual's influence in agonistic interactions.^[105] Being in a coalition allows males to dominate a third individual when they could not by themselves, as politically apt chimpanzees can exert power over aggressive interactions regardless of their rank. Coalitions can also give an individual male the confidence to challenge a dominant or larger male. The more allies a male has, the better his chance of becoming dominant. However, most changes in hierarchical rank are caused by one-on-one interactions though usually of low level aggressive displays.^[103][106] Chimpanzee alliances can be unstable, and one member may suddenly turn on another if it is to his advantage.^[107]

Low-ranking males frequently switch sides in disputes between more dominant individuals. Low-ranking males benefit from an unstable hierarchy and often find increased sexual opportunities if a dispute or conflict occurs.^[105][107] Social hierarchies among adult females tend to be less clearly defined. Nevertheless, the status of an adult female may be important for her offspring.^[108] Females in Taï have also been recorded to form alliances.^[109] While chimpanzee social structure is often referred to as patriarchal, it is not entirely unheard of for females to forge coalitions against males.^[110] There is also at least one recorded case of females securing a dominant position over males in their respective troop, albeit in a captive environment.^[111] Social grooming appears to be important in the formation and maintenance of coalitions. It occurs more often among adult males than either between adult females or between the sexes. Males further up the hierarchy receive more grooming.^[106]

Coalitions of adult male chimpanzees will patrol the boundaries of their home range.^[112] Patrols from smaller groups are more likely to avoid contact with their neighbours. Patrols from large groups even take over a smaller group's territory, gaining access to more resources, food, and females.^[107][113] While it was traditionally accepted that only female chimpanzees immigrate and males remain in their natal troop for life, there are confirmed cases of adult males safely integrating themselves into new communities among West African chimpanzees, suggesting they are less territorial than other subspecies.^[114] West African chimpanzee males are also less aggressive with female chimpanzees in general.^[115] Unusual among animals, but similar to humans, chimpanzees within a community can become more polarized and eventually split into two groups, with one group attacking and raiding the other.^[116] The Gombe Chimpanzee War was one such conflict when a prolonged dominance struggle between two males in a community eventually created separate factions. This was followed by a four year conflict (1974–1977) when one group attacked the other leading to the deaths or disappearances of members of the victim group.^[117] While chimpanzees are popularly thought of as more war-like than bonobos, primatologist Christine Webb concludes that "Through an analysis of various chimpanzee and bonobo sanctuary communities, we've found that variation within the two species is greater than differences between them".^[118] While intra-group rivalry among male chimpanzees to determine alpha-status for mating has been observed within groups, research published in 2026 in Science has extended these observations to state that such rivalry within a group between subgroups of chimpanzees could be observed as battling against each other for dominance within the group.^[116][119]

Mating and parenting

Chimpanzees will mate at any time of the year, although the number of sexually receptive females increases during the dry season as opposed to the wet season.^[120] Females exhibit sexual swellings when respective. Chimpanzees are promiscuous; females mate with several males in their community. Other forms of mating also exist. A community's dominant males sometimes defend reproductive access to females. A male and female can form a consortship and mate outside their community. In addition, females sometimes copulate with males from other communities.^[121][122] This gives females more mating opportunities while maintaining the support of the males in their community.^[122]

The gestation period is eight months.^[44] Mothers provide young with food, warmth, and protection, and teach them certain skills. In addition, a chimpanzee can benefit from its mother's status.^[123][124] Male chimpanzees continue to associate with the females they impregnated and interact with and support their offspring.^[125] Orphaned chimpanzees are occasionally adopted by adult males who can act as effective surrogates and tend to their needs.^[126] Infanticide has been recorded in chimpanzee communities in some areas, and the victims are often consumed. Male chimpanzees practice infanticide on unrelated young to shorten the interbirth intervals in the females.^[127][128] Females sometimes practice infanticide, but this appears to be uncommon.^[108]

Newborn chimpanzees are helpless and rely on their mothers for support, being in physical contact with them around 80% of the time.^[129] Wild chimpanzess are seen to exhibit both "secure" and "insecure" attachment styles, with the offspring looking to the mother for comfort in the former and more independent offspring in the latter. "Disorganised" attachment styles (maladaptive parent-offspring bonds caused by abuse or neglect); researchers are only observed in captive chimpanzees raised around humans.^[130] When they reach five to seven months, infants ride on their mothers' backs and at eight months they begin to spend more time without physical contact but still within arm reach. By four to five years, chimpanzees are weaned.^[129] The juvenile stage lasts between the ages of five to seven years. During this period, chimpanzees walk and feed on their own and sleep by themselves, but remain emotionally bonded to their mothers. After this, the apes become adolescents and begin to transition into their adult roles. Females reach adulthood at around 15 years, and males a year later.^[131]

Communication

Pant-hoot call

Pant-hoot call made by an adult male, demonstrating the introduction, build-up, climax, and let-down phases.

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Chimpanzees use facial expressions, postures, and sounds to communicate with each other. They have expressive faces that are important in close-up communications. When frightened, a "full closed grin" causes nearby individuals to be fearful, as well. Playful chimpanzees display an open-mouthed "smile". Chimpanzees may also express themselves with the "pout", which is made in distress and the "sneer", which signals alarm. When submitting to a dominant individual, a chimpanzee crunches, bobs, and reaches its hand out. When in an aggressive mode, a chimpanzee swaggers bipedally, hunched over and arms swinging, in an attempt to exaggerate its size.^[132] Chimpanzees beat their hands and feet against the trunks of large trees, an act that is known as "drumming". They also do this when traveling, displaying, begging and when they see individuals from other communities.^[133]

Vocalisations are also important in chimpanzee communication. The most common call in adults is the "pant-hoot", which can be made in numerous contexts including meetings, feedings and travelling. Pant-hoots are made of four parts, starting with soft "hoos", the introduction; that gets louder and louder, the build-up; and climax into screams and sometimes barks; these die down back to soft "hoos" during the letdown phase as the call ends.^[133][134] Grunting is made in situations like feeding and greeting.^[133] Submissive individuals make "pant-grunts" towards their superiors.^[108][135] Whimpering is made by young chimpanzees as a form of begging or when lost from the group.^[133] Chimpanzees use distance calls to draw attention to danger, food sources, or other community members.^[136] "Barks" come in two forms: "short barks" which are made during hunts and "tonal barks" which are a reaction to large snakes.^[133]

Hunting

Chimpanzees hunt tree-dwelling monkeys in groups or alone. At Taï, members of a hunting group assume different roles. "Drivers" will herd prey into a certain direction without actually catching them. "Blockers" are stationed at the bottom of the trees and climb up to block prey that takes off in a different direction. "Chasers" will pursue and isolate a monkey while trying to catch it. Finally, "ambushers" hide and rush out when a monkey nears. At Gombe, chimpanzees may hunt alone, selecting areas with less continuous tree canopies where they can more easily corner their prey.^[137] While both adults and infants are taken, adult male colobus monkeys will attack the hunting chimpanzees.^[138] When caught and killed, the meal is distributed to all hunting party members and even bystanders.^[137]

Male chimpanzees hunt in groups more than females. Female chimpanzees tend to hunt solitarily. If a female chimpanzee were to participate in the hunting group and catch a red colobus, it would likely immediately be taken by an adult male. Female chimpanzees are estimated to hunt around 10–15% of a community's vertebrates.^[139]

Tool use

Nearly all chimpanzee populations have been recorded using tools, typically made of sticks, rocks, grass, and leaves, to forage for food and water. They show evidence of planning and foresight, despite their rudimentary and simple quality.^[142] Chimpanzees have used stone tools since at least 4,300 years ago.^[156]

In 1960, a chimpanzee from the Kasakela chimpanzee community was the first nonhuman animal reported making a tool, by modifying a twig to use as an instrument for extracting termites from their mound.^[157][158] Chimpanzees living in Tanzania were found to deliberately choose plants that provide materials that produce more flexible tools for termite fishing.^[159] At Taï, chimpanzees simply use their hands to extract termites.^[142] When foraging for honey, chimpanzees use longer sticks when extracting honey from the hives of dangerous African honeybees, as opposed to those of stingless bees.^[160] Chimpanzees also fish for ants using the same tactic. West African chimpanzees crack open hard nuts with stones or branches. Some pre-planning in the gathering of these tools is apparent, as they are not found together or where the nuts are collected. Both nut cracking and ant dipping are difficult to learn.^[142][161] Chimpanzees also use leaves as sponges or spoons to drink water.^[162]

West African chimpanzees in Senegal were found to sharpen sticks with their teeth, which were then used to spear Senegal bushbabies out of small holes in trees.^[163] An eastern chimpanzee has been observed using a modified branch as a tool to capture a squirrel.^[164] In 2020, experimental studies on captive chimpanzees have found that many of their species-typical tool-use behaviour can be individually learnt by chimpanzees.^[165] However, in comparing hypothesized early hominid making and use of stone flakes, a 2021 study on comparable abilities in chimpanzees did not find this behaviour across two populations of chimpanzees—suggesting that this behaviour is outside the chimpanzee species-typical range.^[166]

Speech and language

Scientists have attempted to teach human language to several species of great ape. One early attempt by Allen and Beatrix Gardner in the 1960s involved spending 51 months teaching American Sign Language to a chimpanzee named Washoe. The Gardners reported that Washoe learned 151 signs, and had spontaneously taught them to other chimpanzees, including her adopted son, Loulis.^[167] Over a longer period of time, Washoe was reported to have learned over 350 signs.^[168]

Debate is ongoing among scientists such as David Premack about chimpanzees' ability to learn language. Since the early reports on Washoe, numerous other studies have been conducted, with varying levels of success.^[169] One involved a chimpanzee jokingly named Nim Chimpsky (in allusion to the theorist of language Noam Chomsky), trained by Herbert S. Terrace of Columbia University. Although his initial reports were quite positive, in November 1979, Terrace and his team, including psycholinguist Thomas Bever, re-evaluated the videotapes of Nim with his trainers, analyzing them frame by frame for signs, as well as for exact context (what was happening both before and after Nim's signs). In the reanalysis, Terrace and Bever concluded that Nim's utterances could be explained merely as prompting on the part of the experimenters, as well as mistakes in reporting the data. "Much of the apes' behaviour is pure drill", he said. "Language still stands as an important definition of the human species". In this reversal, Terrace now argued Nim's use of ASL was not like human language acquisition. Nim never initiated conversations himself, rarely introduced new words, and mostly imitated what the humans did. More importantly, Nim's word strings varied in their ordering, suggesting that he was incapable of syntax. Nim's sentences also did not grow in length, unlike human children whose vocabulary size and sentence length show a strong positive correlation.^[170] Chomsky has voiced opposition to the viewpoint of Terrace and Bever based upon his theory of the inheritance of language capacity as being limited to human inheritance alone among all animals.^[171]

In culture and entertainment

The Gio people of Liberia and the Hemba people of the Congo make chimpanzee masks. Gio masks are relatively primitive, and worn when warning young people about bad behaviours. The Hemba masks have a smile perceived as disturbing, and are worn at funerals to represent the "awful reality of death". The masks may also decorate homes for protection and promote fertility, for both humans and plants. Stories have been told of chimpanzees kidnapping and raping women.^[172]

In Western popular culture, chimpanzees have occasionally been stereotyped as childlike and comical due to their appearance and movements, which humans often find amusing. Chimpanzees in media are often sidekicks including Judy on the television series Daktari in the 1960s and Darwin on The Wild Thornberrys in the 1990s. Chimpanzee characters and actions are rarely relevant to the plot. Depictions of chimpanzees as individuals rather than stock characters, and as central rather than incidental to the plot can be found in science fiction. Robert A. Heinlein's 1947 short story "Jerry Was a Man" concerns a genetically enhanced chimpanzee suing for better treatment. The 1972 film Conquest of the Planet of the Apes, the third sequel of the 1968 film Planet of the Apes, portrays a chimpanzee named Caesar leading a rebellion of apes against humanity.^[173] Entertainment acts featuring chimpanzees dressed up as humans with lip-synchronised human voices were common in circuses, stage shows and TV shows like Lancelot Link, Secret Chimp (1970–1972) and The Chimp Channel (1999).^[173]

From 1926 until 1972, London Zoo, followed by several other zoos around the world, held a chimpanzees' tea party daily.^[174][175] Animal rights groups have urged a stop to such acts, considering them abusive.^[176]

Attacks

Chimpanzees have attacked humans.^[177][178] In Uganda, several attacks on children have happened, some of them fatal. Some of these attacks may have been due to the chimpanzees being intoxicated (from alcohol obtained from rural brewing operations) and becoming aggressive towards humans.^[179] Human interactions with chimpanzees may be especially dangerous if the chimpanzees perceive humans as potential rivals.^[180] At least six cases of chimpanzees snatching and eating human babies are documented.^[181]

A chimpanzee's strength and sharp teeth mean that attacks, even on adult humans, can cause severe injuries. This was evident after the attack and near death of former NASCAR driver St. James Davis, who was mauled by two escaped chimpanzees while he and his wife were celebrating the birthday of their former pet chimpanzee.^[182][183] Another example of chimpanzees being aggressive toward humans occurred in 2009 in Stamford, Connecticut, when a 90-kilogram (200 lb), 13-year-old pet chimpanzee named Travis attacked his owner's friend, who lost her hands, eyes, nose, and part of her maxilla from the attack.^[184][185]

In captivity

Chimpanzees are more numerous in captivity than other great ape species, with facilities in the US alone housing around 1300 individuals as of 2024. Captive chimpanzees reside in research facilities, zoos and sanctuaries, the latter of which have been used for individuals retired from laboratories. Modern facilities try to stimulate the ape's natural behaviours and cognitive abilities, using tools like feeders, termite mounds, climbable surfaces and plastic toys, as well as material to build nests. Chimpanzees are also able to bond with their human caretakers though barriers.^[186] Even with enrichments captive chimpanzees can exhibit abnormal behaviours such as eating and drinking their own faeces and urine, plucking hair, repetitive rocking and even self-mutilation.^[187]

Hundreds of chimpanzees have been kept in laboratories most of which either conduct or make the animals available for invasive research,^[188] defined as "inoculation with an infectious agent, surgery or biopsy conducted for the sake of research and not for the sake of the chimpanzee, and/or drug testing".^[189] Research chimpanzees tend to be used repeatedly over decades for up to 40 years, unlike the pattern of use of most laboratory animals.^[190] Two federally funded American laboratories use chimpanzees: the Yerkes National Primate Research Center at Emory University in Atlanta, Georgia, and the Southwest National Primate Center in San Antonio, Texas.^[191] Five hundred chimpanzees have been retired from laboratory use in the US and live in sanctuaries in the US or Canada.^[188] A five-year moratorium was imposed by the US National Institutes of Health in 1996, because too many chimpanzees had been bred for HIV research, and it has been extended annually since 2001.^[191] With the publication of the chimpanzee genome, plans to increase the use of chimpanzees in America were reportedly increasing in 2006, some scientists arguing that the federal moratorium on breeding chimpanzees for research should be lifted.^[191][192] However, in 2007, the NIH made the moratorium permanent.^[193]

Other researchers argue that chimpanzees either should not be used in research, or should be treated differently, for instance with legal status as persons.^[194] Pascal Gagneux, an evolutionary biologist and primate expert at the University of California, San Diego, argues, given chimpanzees' sense of self, tool use, and genetic similarity to human beings, studies using chimpanzees should follow the ethical guidelines used for human subjects unable to give consent.^[191] A recent study suggests chimpanzees which are retired from labs exhibit a form of post-traumatic stress disorder.^[195] Stuart Zola, director of the Yerkes laboratory, disagrees. He told National Geographic: "I don't think we should make a distinction between our obligation to treat humanely any species, whether it's a rat or a monkey or a chimpanzee. No matter how much we may wish it, chimps are not human."^[191]

As of 2025, there are no labs in Europe holding chimpanzees for research purposes. Historically, there was only one European laboratory, the Biomedical Primate Research Centre in Rijswijk, the Netherlands, used chimpanzees in research. It formerly held 108 chimpanzees among 1,300 non-human primates. The Dutch ministry of science decided to phase out research at the centre from 2001.^[196] Trials already under way were however allowed to run their course.^[197]

As of 2021, 12 chimpanzees were held in Kyoto including the female Ai which have been studied at the Primate Research Institute of Kyoto University, Japan, formerly directed by Tetsuro Matsuzawa, since 1978.^[198] Two chimpanzees have been sent into outer space as NASA research subjects. Ham, the first great ape in space, was launched in the Mercury-Redstone 2 capsule on 31 January 1961, and survived the suborbital flight. Enos, the third primate to orbit Earth after Soviet cosmonauts Yuri Gagarin and Gherman Titov, flew on Mercury-Atlas 5 on 29 November of the same year.^[199][200]

Chimpanzees have traditionally been kept as pets in a few African villages, especially in the Democratic Republic of Congo. In Virunga National Park in the east of the country, the park authorities regularly seize chimpanzees from people keeping them as pets.^[201] Outside their range, chimpanzees are popular as exotic pets despite their strength and aggression. Even in places where keeping non-human primates as pets is illegal, the exotic pet trade continues to prosper, leading to injuries from attacks.^[202]

Field study

Jane Goodall undertook the first long-term field study of the chimpanzee, begun in Tanzania at Gombe Stream National Park in 1960.^[203] Other long-term studies begun in the 1960s include Adriaan Kortlandt's in the eastern Democratic Republic of the Congo and Toshisada Nishida's in Mahale Mountains National Park in Tanzania.^[204][205] Current understanding of the species' typical behaviour and social organisation has been formed largely from Goodall's ongoing 60-year Gombe research study.^{[206][207][208]}

Goodall researched common chimpanzee social and family life beginning with the Kasakela chimpanzee community in Gombe Stream National Park, Tanzania, in 1960, and documented much original commentary about their experienced emotional life.^[209][210] She found that "it isn't only human beings who have personality, who are capable of rational thought [and] emotions like joy and sorrow". She also observed behaviour often considered human, such as hugs, kisses, pats on the back, and even tickling. Goodall insisted that these gestures are evidence of "the close, supportive, affectionate bonds that develop between family members and other individuals within a community, which can persist throughout a life span of more than 50 years".^[210]

Human immunodeficiency virus

Two primary classes of human immunodeficiency virus (HIV) infect humans: HIV-1 and HIV-2. HIV-1 is the more virulent and easily transmitted, and is the source of the majority of HIV infections throughout the world; HIV-2 occurs mostly in west Africa.^[211] Both types originated in west and central Africa, jumping from other primates to humans. HIV-1 has evolved from a simian immunodeficiency virus (SIVcpz) found in the subspecies P. t. troglodytes of southern Cameroon.^[212][213] Kinshasa, in the Democratic Republic of Congo, has the greatest genetic diversity of HIV-1 so far discovered, suggesting the virus has been there longer than anywhere else. HIV-2 crossed species from a different strain of HIV, found in the sooty mangabey monkeys in Guinea-Bissau.^[211]

The oral polio vaccine AIDS hypothesis (OPV AIDS) is a largely discredited hypothesis which argued the AIDS pandemic originated from live polio vaccines prepared in Common chimpanzee tissue cultures, accidentally contaminated with simian immunodeficiency virus and then administered to up to one million Africans between 1957 and 1960 in experimental mass vaccination campaigns. Originally, a few scientists, notably the evolutionary biologist W. D. Hamilton, thought the hypothesis required serious investigation, but they received little support from the scientific community.^[214] In 2003, Hooper published additional statements that he believed supported his hypothesis in an article in the London Review of Books. In his subsequent book, Hooper also stated that Gaston Ninane was involved in using chimpanzee cells to produce vaccine in Congo. Ninane responded to this allegation by stating that he could "categorically deny" ever having tried to make tissue cultures from chimpanzee cells.^[215] The people involved in vaccine production and distribution from America state that no vaccine was prepared locally in Congo and that only the CHAT vaccine from America was used. Barbara Cohen, the technician who was responsible for running the American laboratory that produced this vaccine stated: "At no time did I ever receive or work on chimpanzee kidneys, nor to my knowledge cells derived from chimpanzees. I never made, nor do I know of anyone in the lab who made polio vaccine in chimpanzee cells."^[216] In 2004, the Origin of Aids, a French TV documentary strongly supportive of the OPV hypothesis, appeared on several television stations around the world.^[217]