Svante Pääbo, Neanderthal Man: In search of lost genomes 275pp. Basic Books. £16.99.
If you have ancestors from Europe, Western Asia or the Near East – the places where Neanderthals once lived – you probably have a few Neanderthal genes. That was Richard Leakey’s best guess back in The Making of Mankind (1981). Addressing the question of why, between 30,000 and 40,000 years ago, the Neanderthals disappeared, he contrasted the “Neanderthal phase” theory, on which they gradually evolved into modern humans, with the “Garden of Eden” theory, which supposed modern humans to have evolved in full, maybe in Africa, before spreading around the world, driving to extinction the Neanderthals met en route. Leakey reckoned the evidence favoured an Edenic beginning for modern humans, but not a violent demise for the Neanderthals: they most likely vanished through interbreeding with their invaders.
More than thirty years later, Svante Pääbo has become famous for leading the project that showed this compromise view to be correct. Neanderthal Man is Pääbo’s memoir of his career as a hunter of “ancient DNA”, culminating in the publication, in 2010, of a draft of the DNA sequence of the Neanderthal genome. There is no mention of Leakey, and generally Pääbo gives the impression that, until the sequencing work was well underway, he had not really considered the possibility that Neanderthal genes persist. Certainly the press received the announcement as surprising news. “Neanderthal genes ‘survive in us’” was how the BBC, quoting Pääbo, summed it up. Since that time, the Neanderthal sequence has made possible new kinds of research, and new kinds of headline – often with a familiar ring. The “diabetes risk gene” is, it seems, “‘from Neanderthals’”. They recently got the blame on a grander scale: “Neanderthals gave us disease genes”.
Like James Watson’s The Double Helix (1968), Neanderthal Man is a coming-of-age story, as well as a somewhat disillusioning study of science in the making – though it is set in a professional world very different from the one Watson depicted. As scientific mysteries go, the order of nucleotides in the Neanderthal genome is not quite up in the double-helix league, nor are its implications as consensus-shattering as Pääbo suggests. But the amazing frankness that Watson brought to his tale is present throughout, on everything from Pääbo’s youthful bisexuality to his anxieties about his scientific rivals, and what he calls the “dirty little secret of genomics”: that we “still know next to nothing about how a genome translates into the particularities of a living and breathing individual”.
Pääbo, born and raised in Sweden, came to the study of ancient DNA in the early 1980s not as a paleoanthropologist but as a medic who, unable to shake an earlier interest in Egyptology, wondered whether recoverable DNA survived in mummies. On finding that it did, he went on to extract and sequence DNA from an ever-expanding range of extinct humans and non-humans. Around the mid-1990s his focus shifted towards Neanderthals. Part of the appeal was the prospect of throwing new light on human evolution. But there was also a sense that the recovery and analysis of DNA from Neanderthal fossils offered a formidable but not impossible technical challenge. His team’s first successful sequencing of Neanderthal DNA came in 1996. Ten years later, Pääbo – by then the head of a research group at the Max Planck Institute for Evolutionary Anthropology in Leipzig – announced the launch of an international Neanderthal genome project, an ancient-DNA counterpart to the Human Genome Project.
How to be sure that a Neanderthal gene apparently identical to a modern human gene is not actually a modern human gene, or a human-like bacterial gene, accidentally mixed in to the sample? Contamination is the spectre that haunts ancient DNA studies. There are an alarmingly large number of routes by which alien DNA can insinuate itself and go undetected. The scale of the problem Pääbo faced became vivid for him on meeting with a museum curator who, when asked whether a fossil bone in his keeping had been varnished, gave it a lick. Pääbo’s dread of publishing contaminated results, and the obsessiveness and inventiveness required to avoid doing so, are major themes of Neanderthal Man. Even so, he is open about how much his success has depended not just on being cautious, and having a reputation for being cautious, but on knowing when to ease up.
That “Neanderthal genes survive in us” seems a simple enough claim, and it is tempting to assume the research behind it to be a high-tech version of having a look. Neanderthal Man’s details put paid to any such naivety. At every step of the inquiry Pääbo reveals complex interpretations, of data, machines and people, often combined, as when he has to decide how similar two DNA sequences must be to count as “the same”, whether those criteria have been fulfilled, and who gets to say. Any book that gives a backstage view of a professional life risks reading like an amplified work diary. But what Pääbo achieves by plunging the reader into the minutiae – and what he could have achieved in no other way – is to remove the aura of straightforwardness that clings to scientific facts like the one which he has so assiduously made his own.
Gregory Radick is Professor of History and Philosophy of Science at the University of Leeds and the author of The Simian Tongue: The Long Debate about Animal Language, 2007. He is working on a new history of the birth of genetics.