About 150,000 years ago, along the Congo River, a tryst with a long history took place. Chimpanzees and bonobos – two distinct groups of great apes that share almost all of their DNA with our own species – got together, causing their genetics to become somewhat entwined.
Writing in the journal Science, an international team of geneticists explain that this cross-breeding first occurred sometime between 200,000 and 550,000 years ago. The cumulative effect of these two phases of friskiness mean that certain groups of modern chimpanzees derive 1 percent of their genetic material from bonobos.
This study was conducted as part of a conservation effort to better clarify the genetic distribution of both apes. Both are endangered, but a truly accurate assessment of their numbers cannot be conducted without knowing how their DNA is spread over the continent.
By analyzing the entire genomes of 75 chimpanzees and bonobos from 10 countries, the research team could work out whereabouts they had migrated to and from over the course of their evolutionary history.
“This is the largest analysis of chimpanzee genomes to date and shows that genetics can be used to locate quite precisely where in the wild a chimpanzee comes from,” study co-author Dr Chris Tyler-Smith, an evolutionary geneticist from the Wellcome Trust Sanger Institute, said in a statement.
“This can aid the release of illegally captured chimpanzees back into the right place in the wild and provide key evidence for action against the captors.”
Apart from their cross-breeding, the team were startled to discover that they had repeatedly crossed the enormous Congo River, which was previously thought to be a powerful barrier to any such unions.
“It’s reasonable to assume that [back then] the river might have looked very different to how it does today, maybe allowing the populations to meet,” lead author Dr Tomàs Marquès-Bonet, a researcher from the Institute of Biological Evolution at Pompeu Fabra University, told IFLScience.
A bonobo-based argument. Sergey Uryadnikov/Shutterstock