The Ancestor's Tale: A Pilgrimage to the Dawn of Evolution

by Richard Dawkins

The Denisovan’s Tale is short, as befits a set of people about whom we know so little. They are named after the Denisova Cave in the Altai mountains of Siberia, and the cave itself is named after Denis, an eighteenth-century resident hermit. Less than a decade ago, few people would have heard of it, let alone known how to pronounce it.* Now it is centre stage in debates surrounding recent human evolution. In 2009 Johannes Krause and Qiaomei Fu attempted to extract DNA from one half of the tip of a 40,000-year-old finger bone, excavated from deep under the cave floor. An archaeologist at the site is reported to have described it as the ‘most unspectacular fossil I’ve ever seen’. What did turn out to be spectacular, however, was both the degree of DNA preservation, and the subsequent overturning of established views. First to be sequenced was the mitochondrial DNA. This was found to be distinct from both Moderns and Neanderthals. It lies on a much deeper branch of the gene tree. A year or so later it was joined by more mitochondrial DNA extracted from two molar teeth in almost the same layer of the Denisova excavations. The teeth were visibly larger than those of Neanderthals, more like molars in Homo erectus or the earlier hominids† that we will greet further along in our pilgrimage. Now that the fingertip has been pulverised for DNA extraction, the two teeth constitute all the tangible evidence we have of the Denisovans. Although what we have described so far is titillatin...