Geneticists have previously estimated mutation rates by comparing the human genome with the sequences of other primates. On the basis of species-divergence dates gleaned—ironically—from fossil evidence, they concluded that in human DNA, each letter mutates once every billion years. “It’s a suspiciously round number,” says Linda Vigilant, a molecular anthropologist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. The suspicion turned out to be justified.Now it seems that the clock is off by half. This means that a bunch of divergence dates can be recalculated. One is particular is mentioned:
Take the 400,000–600,000-year-old Sima de Los Huesos site in Atapuerca, Spain, which yielded bones attributed to Homo heidelbergensis, the direct ancestors of Neanderthals. Genetic studies have suggested that earlier ancestors of Neanderthals split from the branch leading to modern humans much more recently, just 270,000–435,000 years ago. A slowed molecular clock pushes this back to a more comfortable 600,000 years ago.It isn't a magic bullet, there are still some kinks to be worked out but it has remarkable potential for getting a handle on when the Denisova genome might have arisen.It might also give us a believable figure for the LCA of apes and humans since the current, 5 million year date is plainly not so.