The 2022 Nobel Prize in Medicine was awarded to the Swedish biologist Svante Pääbo “for his discoveries on the genome of extinct hominins and on human evolution”.
Thanks to his research, Pääbo succeeded in reconstructing the genome (i.e. the exact reading of the entire genetic information of a living being) of the Neanderthal, a distant relative of our species. Pääbo was also the discoverer of the Denisovans, a new species of hominins (the subfamily of hominids that includes gorillas, chimpanzees, and humans).
Pääbo’s studies also made it possible to demonstrate the transfer of genes from these now-extinct hominins to Homo sapiens, our species, after the migrations from Africa some 70,000 years ago. Some traces of this gene passage are still visible today, for example in the way our immune system works.
Pääbo is considered the architect of a new scientific discipline, paleogenomics. And his work has been essential in exploring our past history and, above all, in better understanding what makes our species different from others.
Researching our origins is as fascinating as it is complicated. Thanks to paleontologists and archaeologists, we now know that our species appeared in Africa around 300,000 years ago, while our closest relatives – the Neanderthals – evolved outside of Africa and colonized Europe and parts of western Asia, starting around 400,000 years ago until 30,000 years ago when they died out. About 70,000 years ago, groups of Homo sapiens left Africa and reached the Middle East, only to spread across much of the rest of the planet.
Homo sapiens and Neanderthals therefore coexisted in many areas of Europe and Asia for a long time, probably establishing relationships and interactions that have been very important to our history. The problem is that reconstructing events that happened in such distant times is not easy, but DNA analysis of fossils can provide important clues.
By the late 1990s, some research groups had managed to map almost the entire human genome, making it possible to compare different populations of people in terms of their genetic characteristics. However, it was necessary to reconstruct the Neanderthal genome in order to make more accurate comparisons and reconstruct these distant relationships.
Almost from the beginning of his career, Pääbo has been fascinated by the possibility of using genetic analysis techniques to study Neanderthal DNA to confront the difficulties associated with the degradation of genetic material over time. After thousands of years, only a few traces of DNA remain on an artifact and often lead to contamination, for example due to the presence of genetic material from other organisms such as bacteria.
Undeterred, Pääbo worked for years on systems to overcome these difficulties. In the 1990s he devoted himself to studying the DNA of some Neanderthal mitochondria. Mitochondria are cell organelles that contain their own DNA, so their genome is relatively small and contains only part of the cell’s genetic information. On the other hand, it has thousands of copies of the same genetic material and is therefore more likely to find intact parts for analysis work. Pääbo was able to map DNA from a 40,000-year-old find, providing important new elements to show how Neanderthals differ genetically from humans and chimpanzees.
After initial successes with mitochondria, Pääbo decided it was time to try to map the real Neanderthal genome, much larger and more articulated. Together with his research group at the Max Plank Institute in Leipzig (Germany), he perfected new analysis techniques on very old bones and in 2010 managed to publish the first genome of a Neanderthal. From this study, he emerged as the most recent common ancestor of Neanderthals and Homo sapiens about 800,000 years ago.
Pääbo’s studies also allowed to confirm that Neanderthals and Homo sapiens interbred in their millennia-long coexistence, resulting in our species inheriting some traits of the other group. The genome of modern humans of European or Asian descent is estimated to be 1-4 percent of Neanderthal origin.
(Nobel Prize)
But Pääbo’s work was not limited to these studies. With his own research group, he analyzed some bone remains found in 2008 in some caves du Denisova in the Altai Mountains in Siberia. Dating from around 40,000 years ago, they contained well-preserved genetic material, allowing us to hypothesize that they belonged to a never-before-identified hominin species, the “Denisovians.” It was also later discovered that some of their genes had passed to our species,
In combination with other important research, Pääbo’s studies have therefore allowed us to better understand some essential aspects of our evolutionary history. When Homo sapiens first migrated from Africa, at least two distinct populations of hominins were active between Europe and Asia. The Neanderthals lived mainly in the west while the Denisovans lived in the east. As Homo sapiens migrated more and more from Africa, they interbred with Neanderthals and Denisovans and inherited some of their genetic material.
In just under 30 years, Svante Pääbo has had an enormous impact on the history of human evolution and is considered the founder of a new discipline that made this possible, paleogenomics. After the first studies, his research group was able to analyze the genomes of other now extinct hominins. The analyzes and techniques developed by Pääbo will be essential in the years to come, also to confirm or refute the hypotheses of other crossings that took place in Africa before the great migrations of our species.
Svante Pääbo was born in Stockholm in 1955 and received his PhD from Uppsala University in 1986. He has worked at numerous universities and research centers and founded the Max Plank Institute for Evolutionary Anthropology in Leipzig, Germany in 1999.