In Leipzig an international effort led by Svante Pääbo's team at the Max Planck Institute of Evolutionary Anthropology has produced a genome sequence for a Neanderthal woman who lived in Siberia 50 millennia ago. It is of as high a quality as genome records obtained from people alive today. We can see the ancient DNA in as much detail as the modern – and we can now see DNA from the extinct form in most living humans' genomes.
Up until a few years ago, many would not have imagined this would be possible. Pääbo and his colleagues certainly had their crises of doubt when they were trying to compile a first-draft Neanderthal genome. A billion ancient DNA fragments, typically a few dozen units long, had to be compared with the three billion units of the modern human genome. Cleanliness was critical too. It's easy to extract DNA from ancient bones. The trouble is that nearly all of it comes from bacteria and the people who have handled them since their discovery.
Much of Pääbo's book is devoted to the details of the difficulties, and how they were overcome by an awesome combination of technology, ingenuity and persistence. It's a story of how modern high-concept science is done, shot through with the crackle of problem-solving and the hum of project tension, with occasional riffs of annoyance about major scientific journals and people who want dinosaur DNA.
Pääbo evinces little interest in Neanderthals themselves. For him their value lies in what they can tell us about our own distinguishing characteristics. He thinks of our principal ancestors as "the replacement crowd", a surging, driven population of movers and shakers who pioneered their way out of Africa, innovated technologically and left dramatic proof of their imagination on cave walls: in short, the forebears of people like him and his colleagues.
And yet his dazzling work has upended his own expectations, just as it defied the expectations of those who supposed it could never be done. He had imagined the great replacement as total, modern-form humans taking over the world and Neanderthals going extinct, but it turns out that people whose roots lie outside Africa typically carry a per cent or two of Neanderthal DNA in their genomes. His group also identified a new form of ancient human from a finger-bone in a Siberian cave. Its genes are present in modern-day Papuans, among others: how they got there we don't know. At every turn, ancient DNA brings us to the edge of wild surmise.