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Swedish geneticist Svante Pääbo has won the Nobel Prize for medicine for pioneering the use of ancient DNA to unlock secrets about human evolution.
The Nobel Committee said Monday that Pääbo “accomplished something seemingly impossible” when he sequenced the first Neanderthal genome and revealed that Homo sapiens interbred with Neanderthals.
His discovery was made public in 2010, after Pääbo pioneered methods to extract, sequence and analyze ancient DNA from Neanderthal bones. Thanks to his work, scientists can compare Neanderthal genomes with the genetic records of humans living today.
“Pääbo’s seminal research gave rise to an entirely new scientific discipline; paleogenomics,” the committee said. “By revealing genetic differences that distinguish all living humans from extinct hominins, his discoveries provide the basis for exploring what makes us uniquely human.”
Pääbo found that most present-day humans share 1% to 4% of their DNA with Neanderthals, meaning Neanderthals and Homo sapiens must have encountered one another and had children before Neanderthals went extinct around 40,000 years ago.
He has worked as the director of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany since 1997, and is an Honorary Research Fellow at London’s Natural History Museum.
“His major contribution is being a pioneer in recovering ancient DNA and that has been extremely important in the study of human evolution.” Chris Stringer, research lead in human evolution at that museum, told CNN on Monday.
Sensational discovery
Pääbo’s subsequent work extracting DNA from tiny fossil fragments found in a cave in Siberia revealed an equally sensational discovery.
The genome he sequenced showed an entirely new kind of extinct human, called Denisovans after the name of the cave. By comparing Denisovan DNA with the genetic records of modern humans, Pääbo then showed that some populations in Asia and Melanesia inherited up to 6% of their DNA from this enigmatic ancient human.
“I think the Neanderthal genome was his biggest single contribution. It revealed that Neanderthals interbred with us. That was disputed for many years, including by me. But he showed that most of us have ancient DNA (from Neanderthals and/or Denisovans),” Stringer added.
Some of the genetic traces left by encounters with these two ancient humans are of medical relevance today. For example, a Denisovan version of the gene called EPAS1, which confers an advantage for survival at high altitude and is common among present-day Tibetans. Pääbo also found that Neanderthal DNA may play a small role in swaying the course of Covid-19 infection.
“This is an important science discovery in evolutionary biology,” said David Paterson, a professor at Oxford University and the president of The Physiological Society in the United Kingdom.
“Ascribing physiological function to highly conserved mitochondrial genes has been important in our understanding in high-altitude acclimatisation as populations move and adapt to new environments, and how genetic variants affect us on a day-to-day basis in health and disease,” Paterson said in a statement.
Pääbo’s father, biochemist Sune Bergström, was part of a trio that won the Nobel Prize for medicine in 1982.
Early passion
When he first unveiled his findings, Pääbo said that “having a first version of the Neanderthal genome fulfills a longstanding dream.”
However, his childhood passion was Egyptology after he visited Egypt with his mother, according to a 2008 interview. And an early success for Pääbo was when he managed to extract, clone and sequence DNA from an Egyptian mummy – work he did secretly at night while conducting unrelated research for his doctorate.
It took decades for Pääbo to perfect the process for extracting ancient DNA from fossils, because with time DNA chemically modifies and degrades into short fragments. This leaves only trace amount that can be easily contaminated with present-day DNA from bacteria and the humans who handle the fossils.
His methods to extract DNA have also been applied to the bones of long-extinct animals, revealing information about the lives of mammoths, cave bears, giant sloths and many other creatures. His team is working on techniques to extract DNA from cave sediment-- allowing scientists to learn about our early relatives without ever having to find their bones – just the dirt from the caves where they hung out.
Katerina Douka, an assistant professor of archaeological science at the University of Vienna who collaborates with Pääbo, told CNN that his work on ancient DNA was as revolutionary to archaeology as the advent of radiocarbon dating, which won a Nobel Prize in 1960
“He invented the field. He unlocked so many secrets about human evolution,” Douka added.
