Chimpanzees and bonobos are equally close to humans, sharing about 98.7% of our DNA. These two species, both members of the genus Pan, are our nearest living relatives. They diverged from each other roughly 1 to 2 million years ago, and both split from the human lineage an estimated 4.6 to 6.2 million years ago. The genetic distance between humans and either species is essentially identical, at around 1.24%.
Two Species, One Closest Relative
The answer isn’t a single species but a tie. Chimpanzees (Pan troglodytes) and bonobos (Pan paniscus) are so closely related to each other that bonobos weren’t even recognized as a separate species until 1929. Genetically, both sit at the same distance from us. About 1.6% of the human genome is actually closer to the bonobo genome than to the chimpanzee genome, while 1.7% is closer to the chimpanzee than to the bonobo. These tiny asymmetries roughly cancel out, meaning neither species has a clear edge in genetic closeness to humans.
For context, our next closest relative after chimpanzees and bonobos is the gorilla, with an average sequence divergence of about 1.62%, compared to 1.24% for the human-chimpanzee pair. After gorillas come orangutans, then gibbons and siamangs. All great apes and humans belong to the same taxonomic family, Hominidae, a classification that was updated specifically to reflect how closely related we are at the DNA level.
What 1.2% Genetic Difference Actually Means
The often-cited figure of roughly 1.2% divergence comes from comparing non-repetitive stretches of DNA on our autosomes (the non-sex chromosomes). That number holds up well across multiple studies. But the real picture is more nuanced: the divergence isn’t uniform across the genome. Some regions differ by as little as 0%, while others diverge by up to 2.66%. The majority of compared sequences fall between 0.8% and 1.6% divergence.
Different types of DNA also diverge at different rates. Protein-coding regions that directly affect body function show only about 0.8% difference, because harmful mutations there tend to get weeded out by natural selection. Pseudogenes, stretches of DNA that no longer code for anything functional, diverge more freely at around 1.56%. These patterns tell us that the 1.2% figure is a useful average, but the functional differences between human and chimpanzee biology are concentrated in specific, high-impact parts of the genome.
What Changed After the Split
Despite sharing so much DNA, humans look and behave dramatically differently from chimpanzees and bonobos. The human brain is about three times the size of a chimpanzee brain, and our cerebral cortex, the region responsible for memory, attention, and complex thought, contains roughly twice as many cells. These differences trace back to small but powerful changes in the genome.
Geneticists have identified thousands of sequences called human accelerated regions: stretches of DNA that stayed nearly identical across millions of years of mammalian evolution but then changed rapidly on the human lineage after our split from chimpanzees. These regions don’t code for proteins directly. Instead, they act as switches that control when and where genes turn on. Some of these switches influence brain size by speeding up the division of neural stem cells. Others affect traits you might not expect, like the density of sweat glands in human skin, which allowed our ancestors to cool down efficiently during long-distance running. Still others shaped limb development and even aspects of sex-linked behavior.
Chimpanzees and Bonobos Mirror Different Sides of Us
One of the most fascinating things about having two equally close relatives is that they reflect very different aspects of human nature. Chimpanzees live in male-dominated groups and can be intensely competitive. They wage coordinated attacks against rival groups, form political alliances, and use tools in ways that first stunned researchers when Jane Goodall documented them in the 1960s. Traits like empathy, playfulness, and respect for elders have all been traced to our shared ancestry with chimpanzees.
Bonobos take a strikingly different approach. Their communities are led by females, conflicts are often resolved through sexual behavior rather than aggression, and coalitions of females will collectively keep aggressive males in check. Even though the alpha female is typically smaller than the males, the other females rally around her to drive off any male that turns hostile. Bonobo society is notably more peaceful, and it tends to resemble the matriarchal structures that emerge in human societies when there is little direct competition for resources.
The contrast is telling. Human societies swing between cooperation and conflict, between egalitarian and hierarchical structures. Chimpanzees and bonobos each embody one end of that spectrum, suggesting that both tendencies run deep in our shared evolutionary history rather than being unique inventions of the human lineage.
How to Tell Bonobos and Chimpanzees Apart
Bonobos have a more slender, gracile build compared to the stockier, more muscular frame of chimpanzees. From birth, bonobos tend to have dark faces with pink lips and hair that looks as if it were parted down the middle. Chimpanzees are usually born with lighter faces that freckle and darken with age. Bonobos also have proportionally longer legs relative to their torso, giving them a slightly more upright posture when walking on two legs. These physical differences are subtle enough that scientists didn’t formally separate them into two species until 1929, nearly seven decades after chimpanzees were first studied scientifically.
Where Gorillas and Other Apes Fit In
The gorilla lineage branched off from the line leading to humans, chimpanzees, and bonobos an estimated 6.2 to 8.4 million years ago, roughly 1.6 to 2.2 million years before the human-chimpanzee split. Orangutans diverged much earlier, around 12 to 16 million years ago. Gibbons and siamangs split off earlier still and belong to a separate family, Hylobatidae, though they’re part of the same broader superfamily of apes (Hominoidea) that includes us.
So the family tree, from closest to most distant, runs: chimpanzees and bonobos, then gorillas, then orangutans, then gibbons. Every one of these species shares the basic ape body plan with humans: no tail, flexible shoulders, relatively large brains for body size, and extended childhoods. But the chimpanzee and bonobo lineage is, by a comfortable margin, the closest living branch to our own.