The Bonobo territory, criss-crossed with rivers
Bonobos are cousins of the common chimp, famous for being less violent and more sexually liberal than their spear-wielding relatives. Genetic data indicates the two groups diverged around two million years ago; around the same time the Congo river formed and cut them off from one another. But the Congo isn’t the only river in the region and Bonobo territory has been cut up by more rivers (most of which feed the Congo). Might this be leading to another divergence in the chimp family?
Short answer: not yet. A pair of Australian researchers have been looking into variation amongst Bonobo populations isolated by 4 rivers in the region; and whilst they did detect differences in the skull 84-97% of this could be accounted for by within-group variation. In other words, the populations were no more different from each other than from people Bonobos within their own group.
However, they did find an increased level of differences between two of the populations in question. Although nowhere near enough to classify them as a new species (or even sub-species); it does suggest that this branch of the ape family is continuing to evolve and diversify. When we look back at chimps as unchanging representatives of our ancestors, odds are we’re wrong. They evolved too.
Reference
Pilbrow, V., & Groves, C. (2013). Evidence for Divergence in Populations of Bonobos (Pan paniscus) in the Lomami-Lualaba and Kasai-Sankuru Regions Based on Preliminary Analysis of Craniodental Variation. International Journal of Primatology, 1-17.
