An international team of researchers has mapped the genome of the bonobo for the first time, revealing that this great ape shares as much DNA with humans as its more aggressive cousin, the chimpanzee. Identifying and understanding how all three genomes overlap, researchers say, could offer new insights into what makes each species look and behave so differently — despite their near-identical genetic blueprints.
One of the most marked differences between chimps and bonobos is the way each species resolves arguments. Chimps tend to address conflict with violence; bonobos, on the other hand, prefer to settle scores with (non-procreative, sometimes homosexual) sex. When it comes to bonding with others in their group, bonobos are also known to eschew forms of violent male dominance (typical among chimps) in favor of prosocial behavior like food-sharing. Stark behavioral differences such as these have even led scientists to refer to bonobos affectionately as "hippie chimps."
Researchers aren't entirely sure what evolutionary pressures would give rise to such dissimilar social practices, but researchers like Kay Prüfer — bioinformatician at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany and lead author on the bonobo sequencing study, published in today's issue of Nature — believe this behavioral divergence began two million years ago, when populations of the common ancestor of chimps and bonobos were permanently separated by Africa's Congo River. By one million years later, speculates Prüfer, they had evolved into the separate species we know today.
Comparisons of the bonobo genome and sequences of chimps from various populations showed that chimps living just across the Congo River were no more closely related to bonobos than were populations living as far away as Côte d'Ivoire. That implies that the separation was quick and permanent, says Prüfer.
North of the Congo River, the ranges of chimpanzees and gorillas overlap, so those animals compete for food. But no gorillas live south of the river, so bonobos face much less food competition... In the absence of competition, the ancestors of bonobos may have been free to forage a wider range of foods in large groups, and share the spoils freely.
Prüfer and her colleagues suspect that a more detailed explanation of these behavioral differences may be hiding in the species' genomes — not to mention our own. Like chimps, bonobos share 98.7 percent of their genetic blueprint with humans; and while the two great apes are even more closely related to one another than they are to us — sharing 99.6% of their DNA — Prüfer's team also found that "more than three percent of the human genome is more closely related to either the bonobo or the chimpanzee genome than these are to each other." In other words: all three species' genomes are remarkably similar, but some regions — whether it's between chimps and bonobos, bonobos and humans, or humans and chimps — are more similar than others.
How these regions overlap, write the researchers "may eventually help us understand the genetic basis of phenotypes that humans share with one of the two apes to the exclusion of the other." Does that make the bonobo genome "the secret to the biology of peace," as Duke University researcher Brian Hare — who was not involved in the study — described it in an interview with the Associated Press? That's probably a bit of a stretch. But this much is clear: researchers have now mapped the DNA of every species of great ape on Earth (humans, chimps, gorillas, orangutans and bonobos); understanding what parts of our DNA are shared with these species will provide us with some of the best insight possible into what, exactly, makes us human.
The researchers' findings are published in today's issue of Nature.