Ancient DNA has come a long way, baby. We now don’t even need the bones any more to pick up traces of prehistoric beings. This highly sensitive technique for analyzing ancient DNA was announced last week in Science. Studying 85 sediment samples from seven 14,000 to 550,000 year old caves in Europe and Russia, senior author Matthias Meyer and his team of researchers first isolated all DNA from the soil samples. Unsurprisingly, most belonged to bacteria. About 0.05 to 10% belonged to mammals.
The authors then created a targeted enrichment of mitochondrial DNA, a type of bait, to identify the exact DNA to particular species, such as hominins as well as a variety of animals such as the woolly mammoth and woolly rhinos, cave bears and cave hyenas. Neandertal DNA was found in eight archaeological layers from four caves in Eurasia and in the Denisova Cave, they extracted retrieved Denisovan DNA from a Middle Pleistocene layer near the bottom of the stratigraphy. In summary, they were able to tease out DNA of Neanderthals and Denisovans, even when no bones were around! We knew that humans were in the caves because they left behind processed bones or stone tools. This is remarkable given the paleoanthropological fossil record is so sparse.
Obviously, it isn’t perfect as you can’t date the DNA but as long as you date the soil where the DNA was found, you can get a sense of when the hominins lived. Regardless of this caveat and the continuing concern of contamination, this new technique allows us more lines of evidence to see if early humans were present at a site even if we have no bones, because they didn’t have to die to leave a genetic foot print. It can help us could fill blank spots in scientists’ understanding of how and where humans lived and in what ecological contexts, as well.