Nobel Prize in medicine recognizes innovation in ancient DNA study

Swedish scientist Svante Pääbo won the Nobel Prize in medicine Monday for his discoveries on human evolution that provided key insights into our immune system and what makes us unique compared with our extinct cousins, the award’s panel said.

Mr. Pääbo spearheaded the development of new techniques that allowed researchers to compare the genome of modern humans and that of other hominins – the Neanderthals and Denisovans.

While Neanderthal bones were first discovered in the mid-19th century, only by unlocking their DNA – often referred to as the code of life – have scientists been able to fully understand the links between species.

This included the time when modern humans and Neanderthals diverged as a species, determined to be around 800,000 years ago, said Anna Wedell, chair of the Nobel Committee.

“Pääbo and his team also surprisingly found that gene flow had occurred from Neanderthals to Homo sapiens, demonstrating that they had children together during periods of co-existence,” she said.

This transfer of genes between hominin species affects how the immune system of modern humans reacts to infections, such as the coronavirus. People outside Africa have 1-2% of Neanderthal genes.

Mr. Pääbo and his team also managed to extract DNA from a tiny finger bone found in a cave in Siberia, leading to the recognition of a new species of ancient humans they called Denisovans.

Ms. Wedell described this as “a sensational discovery” that subsequently showed Neanderthals and Denisovan to be sister groups which split from each other around 600,000 years ago. Denisovan genes have been found in up to 6% of modern humans in Asia and Southeast Asia, indicating that interbreeding occurred there, too.

“By mixing with them after migrating out of Africa, homo sapiens picked up sequences that improved their chances to survive in their new environments,” said Ms. Wedell. For example, Tibetans share a gene with Denisovans that helps them adapt to the high altitude.

“Svante Pääbo has discovered the genetic make up of our closest relatives, the Neanderthals and the Denison hominins,” Nils-Göran Larsson, a Nobel Assembly member, told the Associated Press after the announcement.

“And the small differences between these extinct human forms and us as humans today will provide important insight into our body functions and how our brain has developed.”

Mr. Pääbo said he was surprised to learn of his win on Monday.

“So I was just gulping down the last cup of tea to go and pick up my daughter at her nanny where she has had an overnight stay, and then I got this call from Sweden and I of course thought it had something to do with our little summer house in Sweden. I thought, ‘Oh the lawn mower’s broken down or something,’” he said in an interview posted on the official home page of the Nobel Prizes.

He mused about what would have happened if Neanderthals had survived another 40,000 years. “Would we see even worse racism against Neanderthals, because they were really in some sense different from us? Or would we actually see our place in the living world quite in a different way when we would have other forms of humans there that are very like us but still different,” he said.

Mr. Pääbo performed his prizewinning studies in Germany at the University of Munich and at the Max Planck Institute for Evolutionary Anthropology in Leipzig. He is the son of Sune Bergstrom, who won the Nobel prize in medicine in 1982. According to the Nobel Foundation, it’s the eighth time that the son or daughter of a Nobel laureate also won a Nobel Prize.

Scientists in the field lauded the Nobel Committee’s choice this year.

David Reich, a geneticist at Harvard Medical School, said he was thrilled the group honored the field of ancient DNA, which he worried might “fall between the cracks.”

By recognizing that DNA can be preserved for tens of thousands of years – and developing ways to extract it – Mr. Pääbo and his team created a completely new way to answer questions about our past, Mr. Reich said. That work was the basis for an “explosive growth” of ancient DNA studies in recent decades.

“It’s totally reconfigured our understanding of human variation and human history,” Mr. Reich said.

Dr. Eric Green, director of the National Human Genome Research Institute, called it “a great day for genomics,” a relatively young field first named in 1987.

The Human Genome project, which ran from 1990-2003, “got us the first sequence of the human genome, and we’ve improved that sequence ever since,” Dr. Green said. Since then, scientists developed new cheaper, extremely sensitive methods for sequencing DNA.

When you sequence DNA from a fossil millions of years old, you only have “vanishingly small amounts” of DNA, Dr. Green said. Among Mr. Pääbo's innovations was figuring out the laboratory methods for extracting and preserving these tiny amounts of DNA. He was then able to lay pieces of the Neanderthal genome sequence against the human sequencing coming out of the Human Genome Project.

Mr. Pääbo's team published the first draft of a Neanderthal genome in 2009. The team sequenced more than 60% of the full genome from a small sample of bone, after contending with decay and contamination from bacteria.

“We should always be proud of the fact that we sequenced our genome. But the idea that we can go back in time and sequence the genome that doesn’t live anymore and something that’s a direct relative of humans is truly remarkable,” Dr. Green said.

Katerina Harvati-Papatheodorou, professor of paleoanthropology at the University of Tübingen in Germany, said the award also underscores the importance of understanding humanity’s evolutionary heritage to gain insights about human health today.

“The most recent example is the finding that genes inherited from our Neanderthal relatives ... can have implications for one’s susceptibility to COVID infections,” she said in an email to the AP.

The medicine prize kicked off a week of Nobel Prize announcements. It continues Tuesday with the physics prize, with chemistry on Wednesday, and literature on Thursday. The 2022 Nobel Peace Prize will be announced on Friday and the economics award on Oct. 10.

Last year’s medicine recipients were David Julius and Ardem Patapoutian for their discoveries into how the human body perceives temperature and touch.

The prizes carry a cash award of 10 million Swedish kronor (nearly $900,000) and will be handed out on Dec. 10. The money comes from a bequest left by the prize’s creator, Swedish inventor Alfred Nobel, who died in 1895.

This story was reported by The Associated Press. Jordans reported from Berlin. Ungar reported from Louisville, Kentucky. Maddie Burakoff contributed from New York.