Swedish Scientist Wins Nobel Prize in Medicine and Physiology

Swedish geneticist Svante Pääbo wins the 2022 Nobel Prize in Medicine and Physiology for his discoveries concerning the genomes of extinct hominins and human evolution.

Pääbo won the 10m Swedish kronor ($896,306) prize, which was announced by the Royal Swedish Academy of Sciences in Stockholm on Monday.

According to the Nobel Assembly at Karolinska Institutet, Pääbo won the prize for sequencing the genome of the Neanderthal, an extinct relative of present-day humans. He also made a discovery of a previously unknown hominin, Denisova. Moreover, Pääbo’s research led to the creation of a new scientific discipline, paleogenomics.

“Importantly, Pääbo also found that gene transfer had occurred from these now extinct hominins to Homo sapiens following the migration out of Africa around 70,000 years ago. This ancient flow of genes to present-day humans has physiological relevance today, for example affecting how our immune system reacts to infections,” the press release says.

The first sequence of Neanderthals

In 1990, Pääbo started analyzing DNA from Neanderthal mitochondria – organelles in cells that contain their own DNA. Using refined methods, the scientist managed to sequence a region of mitochondrial DNA from a 40,000-year-old piece of bone. As a result, he made a sequence of Neanderthals available for the first time ever.

However, the analyses of the small mitochondrial genome gave only limited information. Therefore, Pääbo and his team in the newly established Max Planck Institute improved the methods to isolate and analyze DNA from archaic bone remains.

Using new technological developments that significantly improved the sequencing of DNA, scientists published the first Neanderthal genome sequence in 2010. Comparative analyses demonstrated that the most recent common ancestor of Neanderthals and Homo sapiens lived around 800,000 years ago.

“Comparative analyses showed that DNA sequences from Neanderthals were more similar to sequences from contemporary humans originating from Europe or Asia than to contemporary humans originating from Africa.

This means that Neanderthals and Homo sapiens interbred during their millennia of coexistence. In modern-day humans of European or Asian descent, approximately 1-4% of the genome originates from the Neanderthals,” according to the press release.

Discovery of Denisova

In 2008, a 40,000-year-old fragment from a finger bone was discovered in the Denisova cave in southern Siberia. The bone contained exceptionally well-preserved DNA, which Pääbo’s team sequenced. The scientists found that the DNA sequence was different from all known sequences from Neanderthals and present-day humans.

This is how a previously unknown hominin was discovered and given the name Denisova. Moreover, Pääbo and his team found that gene flow had also occurred between Denisova and Homo sapiens. This relationship was first seen in populations in Melanesia and other parts of South East Asia, where individuals carry up to 6% Denisova DNA.

“Pääbo’s discoveries have generated a new understanding of our evolutionary history. At the time when Homo sapiens migrated out of Africa, at least two extinct hominin populations inhabited Eurasia. Neanderthals lived in western Eurasia, whereas Denisovans populated the eastern parts of the continent.

During the expansion of Homo sapiens outside Africa and their migration east, they not only encountered and interbred with Neanderthals, but also with Denisovans,” the press release says.

Resources:

The Nobel Prize. Press release: The Nobel Prize in Physiology or Medicine 2022.

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