Scientists have succeeded to decode the bonobo genome, the biochemical instructions in the ape’s cells that guide the building and maintenance of the animal’s body.
It is the last great ape to have its DNA sequence laid bare, following the chimpanzee, orangutan and gorilla.
Comparisons of all their codes, including the human genome, will shed new light on the biology and evolution of these closely related species.
The sequencing and analysis work is reported in the journal Nature.
It was undertaken by an international team led from the Max Planck Institute (MPI) for Evolutionary Anthropology in Leipzig, Germany.
The samples for study were taken from a female bonobo known as Ulindi which resides in Leipzig zoo.
Bonobos (Pan paniscus), together with chimpanzees (Pan troglodytes), are the closest living relatives of humans.
If one compares the DNA “letters” in the sequences of all three species, there is only a 1.3% difference between humans and their ape cousins.
The separation between the bonobo and the chimp is smaller still. Only four letters in every thousand is changed.
“Based on the differences that we observe between the genomes, one can actually estimate when the last common ancestor between these species lived,” explained MPI’s Kay Prufer.
“And between chimpanzees and bonobos that is maybe a million years in the past. For the chimps, bonobos, and humans – the common ancestor of all three lived somewhere around four to five million years ago,” he said.
Bonobos and chimpanzees live very near to each other in central Africa, but their populations are separated by the Congo River.
Indeed, it has long been thought that the creation of the river about two million years ago was responsible for the divergence of the species. And the new analysis certainly seems to support that hypothesis, with no significant signal of interbreeding detected in the DNA of the apes.
“It seems there was a very clean split,” said Dr. Kay Prufer.
But as similar as their genomes are, bonobos and chimps do display some quite diverse behaviors.
Chimps are very territorial and resort to aggressive actions to resolve conflicts, whereas bonobos are more placid and will use sex as a tool to settle their differences.
The researchers want to learn something about the origin of these behaviors, and the degree to which they are influenced by genetics.
“That’s the great hope,” said Dr. Kay Prufer.
“If you look at bonobos, chimpanzees and humans, what you can see is that there are some specific characteristics that we share with both of them.
“So, for instance, the non-conceptive sexual behavior is a trait that is certainly shared with bonobos, while the aggressive behavior unfortunately is also a trait that is shared with chimpanzees.
“In a way, it is a question of what the ancestor of all three looked like. Which one actually evolved the new trait here?”
To get at some answers, scientists plan to look more deeply at those parts of the genomes where humans share more similarity to bonobos or chimpanzees. It turns out that that more than 3% of the human genome is more closely related to either the bonobo or the chimpanzee genome than these are to each other.