How Neanderthal sex life was revealed by fossil DNA

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In the late 1980s I visited an exhibition at the Museum of Natural History in New York. Not the impressive permanent collection of dinosaurs, always full of gaping children under the Tyrannosaurus rex, but a small exhibition about what we can learn from examining remains.

The exhibition has been arranged according to the age of the remains. It started with what we can discover by examining a fresh corpse. It explained the work of coroners and coroners. In the next room I learned what one can discover about corpses in the decay; in the other room how it is possible to study mummified bodies, frozen mammoths and ancient corpses kept in swamps. And so the exhibition went on: in each room the corpses got older until we got to the skeletons and finally the fossilized skeletons.

Svante Pääbo, Nobel Prize in Medicine 2022, who studied how to extract DNA from mummies (Reproduction/EFE) Photo: EFE / EFE

The older the corpse, the harder it was to figure out what it was doing before it died. If we find a suicide note in the pocket of a corpse trapped in a river, you can imagine what was going through his mind before dying. But it’s virtually impossible to detect the thoughts in the brain of a Neanderthal skull.

As the exhibition progressed, I sadly became convinced that the mysteries of our distant ancestors were lost and we had to be content with what little information was gleaned directly from the bones. A skull shattered by a blow says something about the violence of death but little about the reasons for the aggression.

In the last room, in a corner, a display showed how some scientists were extracting DNA from prehistoric bones. They used a dental drill to drill a tooth and were able to extract DNA from the pulp. Or extracting DNA from mummies. They found it was sufficiently conserved to be sequenced.

I realized that this could completely change archeology and paleontology. I returned to my lab and searched the library for the works of these scientists who extracted DNA from prehistoric bones. That day I read Svante Pääbo’s first work, his doctoral thesis, in which he showed that it was possible to extract DNA from mummies. This week, Pääbo received the Nobel Prize in Medicine.

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I watched as Pääbo’s early work was discredited because of the possibility that the tiny amounts of DNA he was able to extract were new material that would have contaminated the samples during the procedure. And this has actually been proven in several cases.

But over the next few years, Pääbo managed to perfect the extraction methods and show that the DNA was indeed ancient. With this technological feat, bones are no longer simple macroscopic objects, becoming boxes that hold copies of that creature’s genome. And that revolutionized paleontology. We now have access to the genomes of creatures that died out millions of years ago.

In recent decades, Pääbo has used this technology to study the genomes of hundreds of extinct creatures, but his most important work was sequencing the genome of Neanderthals. They are that other species, our close cousin, with whom we shared the planet until about 30,000 years ago. By comparing our genome to that of Neanderthals, Pääbo’s group discovered that we now have Neanderthal genes. This proved that our ancestors had sex with these cousins. A skeleton of an individual who was the daughter of a human and a Neanderthal was recently discovered.

Who would have thought decades ago that a young graduate student interested in mummies and drilling teeth to extract DNA could discover the sexual behavior of people who died tens of thousands of years ago? Pääbo could have given up trying to extract DNA from mummies and bones when he was crucified by the scientific community, who didn’t believe in the reliability of his methods but insisted, got there and completely changed our knowledge of our ancestors. It definitely deserves the Nobel Prize.