Chimpanzee fossils are thin on the ground. After their lineage parted ways with ours, our human ancestors spent millennia kicking about in arid regions and caves ideal for preserving our remains. The ancestors of modern chimpanzees and bonobos, meanwhile, were hanging out in the lush jungles of central Africa.
“There’s a reason pretty much every image of a paleontologist in the field is in a desert or badlands,” writes paleontologist Dave Hone. Fossils can be found only when we have access to exposed rocks that were formed in the epoch of interest, and so “the rainforests of the Congo… are useless.” Add to that the quick decomposition of bodies in rich, acidic rainforest soil, and you have a huge gap in understanding where our modern cousins come from.
But “genomic fossils” could fill some of that gap. A paper published in Nature Ecology and Evolution this week reports finding the footprint of an extinct ape species in the genome of modern bonobos. That footprint can tell us roughly when these ancient apes must have lived, and where. It can even—with a lot of speculation—hint at some of the characteristics of the “ghost ape.”