By John Upton
Five to seven million years ago, as the climate cooled around them, our ancestors began to shy away from some of their hitherto ilk. The forefathers of ourselves and of the neanderthals stopped sleeping with the foremothers of the bonobos and the chimpanzees, and vice versa. We went our separate evolutionary ways.
While wanderlust scattered our predecessors around the world, the other apes remained exclusively in Africa. Some 2 million years ago, the African landscape was cleaved by a new cascade — the Congo River. Unable to cross this vast waterway, the other apes split into two species. The bonobos lived on the river’s south; the chimpanzees to its north.
With the extinction of the neanderthals 30,000 years ago, these two species of apes became our closest relatives. We share 98.7 percent of our genes with each of these species. Bonobos and chimps, meanwhile, share 99.6 percent of their genome with each other.
But those tiny genetic divergences belie dramatic differences in behavior that developed as the bonobos and chimps evolved into independent species.
The chimpanzees developed and refined the darkest sides of the human character. They rape, they murder, they form gangs and posses that fight deadly battles.
The bonobos, meanwhile, came to adopt our make-love-not-war traits. They frolic and revel in merrymaking from the time they are babies until they die. They live in peaceful matriarchal societies. And they freely sleep with multiple partners to bond and have fun — including with same-sex partners.
The genetic differences and similarities between the three ape species were announced this week in the journal Nature by an international team of scientists after they sequenced a bonobo’s genome for the first time. Human and chimpanzee genomes were sequenced previously.
But the new genetic data doesn’t reveal why the two sides of the human character are divided so dramatically between our two closest relatives. The researchers speculate that our shared ancestor may have exhibited the entire spectrum of behaviors, just like us.
“Chimpanzees and bonobos each possess certain characteristics that are more similar to human traits than they are to one another’s,” the researchers wrote in the paper. “No parsimonious reconstruction of the social structure and behavioural patterns of the common ancestor of humans, chimpanzees and bonobos is therefore possible. That ancestor may in fact have possessed a mosaic of features, including those now seen in bonobo, chimpanzee and human.”