The Closest Relatives of Humans: How Apes and People Share a Common Ancestor

The closest living relatives of humans are the great apes — chimpanzees, bonobos, gorillas, and orangutans — with chimpanzees and bonobos being the nearest of all. Modern science establishes this kinship not only from ape behaviour that so often mirrors our own, but from comparisons of external and internal anatomy, embryonic development, the fossil record, and — most decisively — from DNA. The evidence converges on a single conclusion: Homo sapiens shares a common ancestor with the other apes.

The case that humans descended from apes rests on multiple independent lines of proof, and it draws heavily on ape behaviour that resembles human conduct, as discussed elsewhere. Below we look closely at who these relatives are, what they share with us, and what molecular biology has added to the picture.

Who are humanity's closest relatives?

Humanity's closest relatives are the great apes, a group that includes chimpanzees (Pan troglodytes), bonobos (Pan paniscus), gorillas (Gorilla gorilla), and orangutans (Pongo pygmaeus). Among all living species, the two members of the genus Pan — chimpanzees and bonobos — are genetically the nearest to Homo sapiens. These animals belong to the primate family Hominidae, and their anatomy, physiology, and genome overlap with ours to a striking degree.

It is worth clearing up a common misconception at the outset: humans did not descend from any modern ape. Instead, humans and today's great apes share extinct common ancestors and diverged along separate evolutionary paths. The "ladder of progress" image — in which one living species turns into another in a straight line — misrepresents how evolution works. Living apes are cousins on a branching tree, not rungs on a ladder.

Great apes as the nearest relatives of humans

Unlike most other animals, the great apes — like humans — have no tail. These animals were once called quadrumana ("four-handed") to distinguish them from four-legged lower animals, but that label is inaccurate. In reality the great apes are two-handed and two-legged, a trait that sets them apart from other animals and aligns them with people.

External resemblance between humans and great apes

The physical likeness between humans and the anthropoid apes is immediately visible in the limbs, hands, skin, and even the shape of the ears. These surface similarities were among the earliest observations that led naturalists, including Charles Darwin, to place humans firmly within the primate order.

Absence of a tail and structure of the limbs

Great apes lack a tail and possess two arms and two legs rather than four limbs used identically for locomotion, which is one of the clearest external features linking them to humans. This body plan — an upright-capable torso, mobile shoulders, and grasping hands — distinguishes the apes (family Hominidae) from monkeys and from the lesser apes of the family Hylobatidae, the gibbons.

Nails, palms, and vestigial body hair

Great apes have flat nails on their fingers and toes, palms creased with lines strikingly similar to the patterns on a human palm, and — unlike the largely bare human body — a coat of hair.

Humans, however, retain hair scattered over the whole body (especially in men), a remnant of the coat worn by our ape-like ancestors. Tellingly, even the direction in which the hair grows is the same in the higher apes and in humans.

Shape of the outer ear

The external ears of the great apes are notably like the human ear in form, another of the visible resemblances that link the two.

Internal structure: skeleton, muscles, and organs

When you examine the skeleton, muscles, blood vessels, nerves, brain, and the respiratory and digestive organs of the great apes, they turn out to be remarkably similar to the corresponding body parts and organs in humans. The correspondence runs deeper than surface appearance and reaches into comparative anatomy at every level.

Comparative anatomy of primates

Comparative anatomy documents point-by-point matches in the skeletons of humans and apes — the same bones in the same arrangement, differing mainly in proportion and adaptation. Anatomists such as Zihlman and Diogo have shown that many of the muscles once thought to be uniquely human have close counterparts in chimpanzees, gorillas, and orangutans. Sexual dimorphism, the physical difference between males and females, varies across the family: it is pronounced in gorillas and orangutans, where males are far larger than females, and comparatively modest in bonobos and humans. Body composition also shifted over primate evolution, with humans developing relatively more fat and less muscle mass than chimpanzees of comparable size.

Similar facial muscles and the expression of emotion

The facial (mimetic) musculature of the higher apes and of humans is strikingly alike in structure. This is why apes can register on their faces sensations resembling our own — fright and calm, joy and sorrow, laughter and weeping, and so on.

Conversely, because the facial muscles of the great apes and humans are built so similarly, people are able to imitate certain characteristic ape grimaces. This shared architecture of expression underlies much of the emotional communication seen in both.

Brain structure in humans and apes

The brains of great apes share the same major divisions, lobes, and folding patterns as the human brain, differing chiefly in overall size and in the expansion of the association cortex. The human brain is roughly three times larger than a chimpanzee's, yet the underlying wiring is homologous. Research led by Frans de Waal and colleagues has even identified brain circuits that appear to predispose bonobos toward cooperation and tolerance, while related circuits in chimpanzees are more attuned to competition — a neurological reflection of the two species' contrasting temperaments.

Dental system and dental features

Great apes, like humans, have thirty-two teeth of four kinds: incisors, canines, premolars, and molars. The number and general arrangement of the teeth are shared, though the details differ — apes typically have larger, more projecting canines, whereas human canines are reduced and the dental arch is more rounded. These dental characteristics are so diagnostic that palaeontologists routinely identify and classify fossil primates from isolated teeth alone.

Chemical composition of the blood

The blood of the great apes is very close to human blood in its chemical make-up. This biochemical kinship extends to blood proteins and serum reactions, and it was one of the first pieces of laboratory evidence — long before DNA sequencing — to confirm the tight relationship between humans and the anthropoid apes.

Embryonic development in humans and apes

The early development of a human and a great ape embryo is nearly indistinguishable, another line of evidence for shared ancestry. In the earliest stages of gestation the embryo of a great ape cannot be told apart from that of a human.

Length of gestation and maturation

Great apes are carried in the womb for eight to nine months (a human child, for nine), and the interval between birth and maturity is far longer than in other animals — almost as long as in humans. An orangutan reaches maturity at ten to twelve years, and a gorilla later still. This prolonged childhood, during which the young learn from their group, is itself a shared primate trait tied to large brains and complex social life.

Genetic kinship between humans and apes

Genetics has confirmed and sharpened everything anatomy suggested: humans and great apes carry nearly identical genetic instructions written in DNA. Because DNA is the universal genetic code shared by all living organisms, the degree to which two species' DNA matches provides a direct, quantitative measure of how recently they shared an ancestor. Nothing has strengthened the case for human–ape kinship more than the reading of whole genomes.

Comparison of the human and chimpanzee genome

The human and chimpanzee genomes are roughly 98–99% identical in their protein-coding regions, making Pan troglodytes and its sister species the bonobo (Pan paniscus) the closest living genetic relatives of Homo sapiens. How the exact percentage is calculated depends on the method — whether one counts single-letter substitutions across aligned sequences, includes insertions and deletions, or compares whole chromosomes — which is why published figures range from about 96% to 99%. Even at the lower end, the similarity dwarfs that between humans and more distant primates such as rhesus monkeys.

DNA as a measure of evolutionary relationship

DNA works as an evolutionary clock: because mutations accumulate at a broadly steady rate, the number of differences between two species' sequences reflects the time since they diverged. This principle lets biologists rank relationships objectively rather than by appearance alone, and it consistently places chimpanzees and bonobos nearer to humans than gorillas, gorillas nearer than orangutans, and all of the great apes nearer to one another than to monkeys.

Reading DNA: structure and the genetic code

DNA (deoxyribonucleic acid) is a double-stranded molecule whose four chemical "letters" spell out the instructions for building and running an organism. The same four-letter code is used by bacteria, plants, apes, and people alike — a shared inheritance that is itself powerful evidence for the common origin of all life. Genes are stretches of this code, and every living thing shares a large fraction of its genes with every other, with the shared proportion rising steeply among close relatives.

DNA changes along evolutionary lineages

As lineages split and evolve independently, their DNA slowly changes through mutation, so that each branch accumulates its own distinctive alterations. Comparing which changes two species share and which they don't allows researchers to reconstruct the branching order of the evolutionary tree. Some of these lineage-specific changes are well studied in humans, such as the several genes governing human skin-colour variation, which diversified as populations spread into different latitudes.

Comparative genomics and phylogenetic trees

Comparative genomics turns DNA sequences into phylogenetic trees — branching diagrams that map how species are related. Analysts align sequences from many species and use molecular phylogenetic methods to infer the most likely pattern of descent. This work is not free of pitfalls: researchers including Ebersberger have shown that some genes yield conflicting trees, and specialists such as Kevin Omland of the University of Maryland, Baltimore County have written about systematic error in phylogenomic inference, where analytical bias rather than true history can distort a tree. Careful methods, published in journals such as Systematic Biology, Science, and the Proceedings of the National Academy of Sciences, are used to guard against such errors. The same molecular tools reach far beyond primates: they identify the lungfish and other sarcopterygians as the closest living relatives of the tetrapods, the land vertebrates, and they clarify obscure branches such as the treeshrews (Ptilocercus lowii) and the gliding colugos.

The common ancestor of humans and the great apes

Humans and modern great apes descend from extinct common ancestors, not from one another, and the fossil record together with molecular dating pins down when those ancestors lived. The living apes are the surviving cousins of long-vanished lineages, and reconstructing those lineages is the work of palaeontology.

Palaeontological evidence from fossil apes

Palaeontology — the science of extinct organisms that failed to adapt to changing conditions — helps reveal our true ancestors. Scientists have amassed a great many bones of animals long gone from the Earth, including the bones of extinct apes, usually in the form of scattered skeletal fragments and teeth. With today's comparative anatomy, even isolated bones can be used to reconstruct the appearance of the creatures they belonged to.

Long ago scientists worked out the law of correlation of an animal's parts and organs. It is known, for example, that predatory animals have sharp canines and claws and never bear horns or hooves. Conversely, the feet of all herbivores are equipped with hooves, and nearly all ruminants have cloven hooves. The renowned comparative anatomist and palaeontologist Georges Cuvier (1769–1832) used this law of correlation to reconstruct many extinct species.

Cuvier wrote that a single footprint of an animal was enough for him not only to describe its bodily form but also to determine its way of life. A well-known anecdote survives about him. Someone, hoping to frighten Cuvier, fashioned the head of a monstrous horned beast, pulled it on together with an animal skin, and — clacking his teeth the way enraged predators do — crept into Cuvier's room at night. But the scientist was not frightened; he burst out laughing and said:

«I am not afraid of you, monster! You cannot eat me, because you have horns on your head.»

There are, moreover, several fossil species reckoned to be relatives of humans.

Palaeontologists can not only reconstruct the appearance of animals from their bones but, working with geologists — scientists who study the Earth's crust — can also determine when those animals lived. It was established in this way that around fifty million years ago the prosimians (lemurs) appeared on Earth, and some fifteen million years later the earliest lower monkeys (parapithecids) arose. Bones of the ancestors of the great apes (propliopithecids) were found in strata dated to about thirty million years old.

Later still came the anthropoid apes known as dryopithecines. They gave rise to the modern gorilla and chimpanzee and to highly developed fossil apes such as the ramapithecines and australopithecines that connect directly to the human line. Other extinct primates fill out this deep history — Proconsul and Victoriapithecus from the African Miocene, Sivapithecus and the giant Gigantopithecus of Asia, and the puzzling European Oreopithecus.

The common ancestor of humans and chimpanzees

The lineage leading to humans split from the one leading to chimpanzees and bonobos roughly six to eight million years ago, based on both fossil and molecular dating. After that split, the human branch produced a sequence of ancestor forms — Sahelanthropus tchadensis, the genus Ardipithecus, and later the genus Australopithecus — before the appearance of the genus Homo. Chimpanzees and bonobos are therefore not our ancestors but our closest cousins, descended from that same shared population by a separate route.

The African origin of humankind

Human evolution began in Africa, where the oldest hominin fossils and the earliest members of the genus Homo have been found. From East Africa, populations of Homo erectus and later Homo sapiens spread across the continent and eventually throughout the world, which is why modern humans today occupy every inhabited landmass on Earth. This African origin, first argued by Charles Darwin on anatomical grounds, is now confirmed by both fossils and the geographic pattern of human genetic diversity.

Ancient DNA research and the Neanderthals

The recovery of ancient DNA from fossil bones has let scientists read the genomes of extinct humans directly, most famously the Neanderthals (Homo neanderthalensis). This work revealed that Homo sapiens and Neanderthals interbred, so that people of non-African ancestry carry a small percentage of Neanderthal DNA today. Ancient-DNA methods, which map human-specific genetic ancestry across populations, have transformed the study of recent human evolution and repeatedly confirmed the predictions first made from comparing living species' genomes — fossil evidence and molecular evidence pointing to the same history.

Classification of the family Hominidae

Hominidae is the biological family of the great apes, and modern taxonomy — revised as monophyletic groups (branches containing an ancestor and all its descendants) — now places humans firmly inside it. Understanding the classification also means untangling a set of easily confused terms.

Definition and membership of the family

Hominidae, the great ape family, is divided into two subfamilies: Ponginae, containing the orangutans of the genus Pongo, and Homininae, containing gorillas, chimpanzees, bonobos, and humans. Within Homininae, the tribe Hominini groups the genus Homo with the genus Pan. The related terminology is a frequent source of confusion: a hominoid is any ape (including gibbons); a hominid is a member of the great ape family Hominidae; a hominine belongs to the subfamily Homininae; and a hominin is a member of the human tribe Hominini. These definitions have shifted over the decades as classification moved from appearance-based to genetically informed groupings.

The eight living hominid species and four genera

There are eight extant hominid species distributed among four genera:

• Pongo — the orangutans (including Pongo pygmaeus), found in Southeast Asia;
• Gorilla — the gorillas (including Gorilla gorilla), of equatorial Africa;
• Pan — the chimpanzee (Pan troglodytes) and the bonobo (Pan paniscus), of central and West Africa;
• Homo — modern humans (Homo sapiens), now worldwide in distribution.

The geographic distribution of the great apes is telling: every non-human hominid genus is confined to a limited tropical range in Africa or Asia, while Homo sapiens alone spread to inhabit the entire planet — a testament to human behavioural flexibility and adaptability.

The behaviour of humanity's closest relatives

The behaviour of chimpanzees and bonobos — our two closest relatives — spans the full range from organized violence to profound cooperation, and together they illuminate the roots of human conduct. Studying Pan reveals that neither aggression nor altruism is uniquely human.

Aggression and organized violence in chimpanzees

Chimpanzees can be aggressive and even warlike, engaging in coordinated violence between rival groups and maintaining steep dominance hierarchies within them. Jane Goodall's long-term field study first documented chimpanzee tool use — a discovery that overturned the idea that toolmaking set humans apart — and later recorded lethal raids between neighbouring communities. Much of this aggression is driven by competition over resources, territory, and mates. Frans de Waal's classic study Chimpanzee Politics traced the shifting alliances of captive males such as Yeroen, Luit, and Nikkie, showing that chimpanzee power struggles rely on strategy and coalition, not brute force alone.

Cooperation and food sharing among bonobos

Bonobos, in sharp contrast to chimpanzees, are markedly cooperative and readily share food, even with strangers. Where chimpanzees resolve tension through dominance and aggression, bonobos frequently use affiliative and sexual behaviour to defuse conflict and rebuild social bonds. This tolerant, cooperative temperament makes bonobos a valuable counterweight to the chimpanzee model of human origins, suggesting that peaceful coexistence is as much part of our ancestry as competition.

Bonobo social structure and the role of female leaders

Bonobo society is notably female-centred, with coalitions of females holding considerable social power and often outranking individual males. Females cooperate to keep male aggression in check, and social standing frequently passes through the maternal line. Sanctuaries such as Lola ya Bonobo in the Democratic Republic of Congo — the only country where wild bonobos live — have allowed researchers to observe these dynamics closely, confirming a social order strikingly different from the male-dominated hierarchies of chimpanzees.

Bonobo social intelligence compared with chimpanzees

Bonobos and chimpanzees show different profiles of social intelligence, with bonobos tending to excel at reading social and emotional cues and chimpanzees at physical and tool-related problem-solving. Both species meet several cognitive criteria once thought exclusively human, including elements of a theory of mind — the ability to attribute intentions and knowledge to others. Comparative studies suggest that specific brain circuits predispose bonobos toward empathy and cooperation, while related circuitry in chimpanzees leans toward competition and risk-taking.

The evolution of human cooperation and aggression

Humans combine the contrasting tendencies of both Pan species, capable of the coordinated violence seen in chimpanzees and the large-scale cooperation and sharing seen in bonobos. This behavioural duality — the coexistence of altruism and competition in a single species — is a defining feature of Homo sapiens and, uniquely, humans cooperate on a vast scale among unrelated strangers, an ability no other ape approaches. Studying chimpanzees and bonobos side by side helps evolutionary scientists trace where each side of the human character may have come from.

How many features do humans share with apes?

The traits listed above by no means exhaust the kinship between the great apes and humans; in reality there are far more of them. Scientists have counted more than fifty features shared with humans in the orangutan, around ninety in the gorilla, and roughly a hundred in the chimpanzee. Even so, the modern great apes are not the direct ancestors of people — they are our cousins, sharing common ancestry rather than a line of descent.

Why studying related primates matters

Studying our closest primate relatives illuminates human origins, mind, and biology in ways no other subject can, because chimpanzees and bonobos preserve traits and behaviours inherited from our shared ancestors. Insights from this research reach medicine, psychology, and our understanding of what — if anything — is genuinely unique to humans. Books such as Understanding the Tree of Life and academic work published through the Smithsonian Institution and Cambridge University Press keep these questions before both scientists and the public.

Conserving humanity's closest relatives

Every non-human great ape is threatened in the wild, and their close kinship to humans has driven both conservation efforts and debates over their moral status. The Great Ape Project argues for extending basic legal rights — personhood — to great apes, and several jurisdictions now restrict or ban invasive research on them. Sanctuaries such as Chimpanzee Sanctuary Northwest, associated with advocates including J. B. Mulcahy, care for apes retired from laboratories. Protecting these species is not only an ethical duty toward creatures so like ourselves but also a way of preserving living windows onto our own evolutionary past.

Can apes turn into humans?

Modern apes cannot turn into humans, nor humans into apes — science answers this question firmly in the negative. Everything in nature continually changes, evolves, and develops. Not only do animal species change, but so do the conditions of their existence — climate, soil, and vegetation. Just as nothing in nature is unchanging, so there are no absolutely identical objects, no repeated phenomena or events. Humans and the modern great apes, as noted, once had common ancestors — extinct anthropoid apes.

Modern humans and the great apes arose through evolution that proceeded in different directions and lasted millions of years under different conditions. Over that vast span, humans and the great apes moved far apart from one another, and all of nature changed at the same time.

To restore what existed millions of years ago is an unachievable fantasy. No one can bring back yesterday or recover last year's snow, and no one can turn an old man back into a child; such things happen only in fairy tales. An ancient philosopher observed that one cannot step into the same river twice, meaning that the river flows ceaselessly and is therefore constantly changing. A person steps out of the water and wishes to plunge back in, but in that short time the river has already changed, imperceptibly to the human eye — and the person, too, is no longer the same, having also changed.

All of nature, all the life of organisms, may be likened to a river that flows and changes without stop and cannot of itself flow backward. People cannot begin to "develop in reverse" and turn into apes, and, in exactly the same way, modern apes cannot turn into people.