Modern man meets Neanderthal
Text: Marcus Anhäuser
Svante Pääbo relaxes in a chair in his office. “Many people think the interbreeding of humans and Neanderthals is really cool,” he says. He doesn’t deny that he thinks so too, but maintains: “In the long run, it is much more important that we now have a genome from the closest relative of all present-day humans.” Standing behind him is a life-size model of a Neanderthal skeleton.
Pääbo has every reason to relax: He has completed in five years a project that others in the past could only dream of. For the first time ever, scientists have the genome of an extinct member of the genus Homo. The Neanderthals died out some 30,000 years ago. Now that we have their genome sequence, we can delve a little deeper – and not only to find out who or what the Neanderthals were: “Above all, we can describe what changes have occurred in our genome, and some of those must have contributed to making us unique,” says Pääbo. This is a point he makes again and again in every interview. It’s not primarily about the Neanderthals, it’s about us.
Spotlight on paleogenetics
The publication of the Neanderthal genome in the journal Science on May 7, 2010 is a high point in the career of the 55-year-old, the son of Nobel laureate and biochemist Sune Bergström. It is also a highlight for his colleagues and the entire research field of paleogenetics, an area in which he played a pioneering role in the 1980s. Pääbo, who studied Egyptology and then medicine, earning a doctorate in immunology, had yet another research interest: he wanted to decode the DNA of mummies. Nobody had ever done that before. Scientists were not even sure that DNA could be extracted from mummies.
Unbeknownst to his dissertation supervisor, he worked nights on the project. “I was a bit afraid of him, as he might have stopped me from doing it,” recalls Pääbo. When he actually found the DNA in microscopic sections of mummies and was able to stain it and even extract it, he was ecstatic. “Then I had to tell my supervisor,” he remembers with an ironic smile. He submitted his results to Nature and even ended up on the cover of the journal in 1985. It was the perfect start to a career in science.
Following a period in Berkeley, Pääbo was given his own lab at Ludwig Maximilian University in Munich in 1990. It was there, during the mid-1990s, that he studied the DNA of Neanderthals for the first time and found the initial evidence that the “big oaf” was not a direct ancestor of humans. His group had extracted DNA from the mitochondria, the “powerhouses” of the cells. Because many mitochondria are present in each cell, they yield more DNA than the cell nucleus – mitochondrial DNA (mtDNA) can thus be analyzed more easily than nuclear DNA. Neanderthal mtDNA was so different from human mtDNA that it was unlikely that Neanderthals and Homo sapiens had mixed to any large extent.
In 1997, Svante Pääbo moved to Leipzig as one of the five Directors of the new Max Planck Institute for Evolutionary Anthropology in the city. At that time, the focus of the international research community was on sequencing the human genome. The publicly funded human genome project began in the US in 1990 and faced competition from American geneticist Craig Venter’s privately owned biotech company, Celera Genomics, which launched a similar project in 1998. The competitive aspect helped to accelerate the research work. In 2001, both the public and private research efforts were in a position to present a draft version of the human genome. At this stage, nobody even dreamed of reconstructing the entire Neanderthal genome.