Mysterious "ghost apes" may have interbred with the great apes known as bonobos, a relative of chimpanzees and with several surprising human attributes, for hundreds of thousands of years, a new study has found. The situation may have been similar to the case of modern humans that repeatedly had sex with now-extinct human lineages in different parts of the world.
Bonobos (scientific name Pan paniscus), which scientists describe as 'promiscuous' apes, are closely related to chimpanzees (Pan troglodytes) and belong to the same group Pan, just as modern humans and extinct lineages of humans make up the group Homo (Homo sapiens being modern human), an article in LiveScience says.
Geneticists have discovered that ancestors of modern humans often interbred with extinct human lineages such as Neanderthals and Denisovans. The DNA from such genetic mixing continues to influence modern humans, from potential immune boosts to increased risk for depression, obesity, heart attacks, and nicotine addiction, the article says.
Earlier research showed genes likely flowed from bonobos to chimpanzees more than 200,000 years ago, proving their regular interbreeding. Genome analyses of 10 bonobos and 59 chimpanzees have convinced scientists that bonobos, which they consider 'Hippie Chimps' had sex with a now-extinct ape lineage, the Ghost Ape.
"We know humans have interbred with Neanderthals and Denisovans and probably other archaic human populations, and it's interesting to see what happened with our closest living relatives as well," the article quotes study lead author Martin Kuhlwilm, a population geneticist at the Biomedical Research Park of Barcelona, Spain, as saying. The research was first published in the journal Nature.
The researchers were looking for unusual patterns in the ape genomes that would suggest ancient interbreeding with other lineages. This included a hunt for long haplotypes, or sets of DNA sequences seen in one species but not the other, the article says. Long haplotypes are likely inherited from significantly different lineages while short ones are seen as arising from chance mutations within these species. Geneticists look for remnants of long haplotypes. By looking at the length of these odd haplotypes, scientists can estimate how far back the interbreeding occurred.
By isolating this "ghost ape" DNA the researchers reconstructed up to 4.8 per cent of its genome. They said genes in these archaic fragments may have consequences on the workings of the brain, kidneys and immune system of bonobos. Bonobos and chimps are believed to have diverged from each other about 2 million years ago. But, the evidence suggests that the ghost ape diverged from the common ancestor of bonobos and chimps about 3.3 million years ago. Bonobos and the ghost apes must have begun interbreeding sometime between 377,000 and 637,000 years ago. In contrast, chimpanzees never interbred with any now-extinct lineages.