Svante Pääbo: The Surprising Science behind Who We Are and How We Got Here

Its Nobel Prize season- the economics prize will be announced Monday, while most prizes are announced this week. My favorite so far is the Medicine prize being awarded to Svante Pääbo “for his discoveries concerning the genomes of extinct hominins and human evolution”. He figured out how to sequence DNA from Neanderthal remains despite the fact that they were 40,000 years old.

As recently as 2010 it was controversial to suggest that Neanderthals might have mixed with humans, until Pääbo’s DNA definitively settled the debate, showing that “Neanderthals and Homo sapiens interbred during their millennia of coexistence. In modern day humans with European or Asian descent, approximately 1-4% of the genome originates from the Neanderthals”

While the Neanderthal genome settled an existing controversy, Pääbo’s other big discovery came entirely unlooked for. The Nobel Foundation explains:

In 2008, a 40,000-year-old fragment from a finger bone was discovered in the Denisova cave in the southern part of Siberia. The bone contained exceptionally well-preserved DNA, which Pääbo’s team sequenced. The results caused a sensation: the DNA sequence was unique when compared to all known sequences from Neanderthals and present-day humans. Pääbo had discovered a previously unknown hominin, which was given the name Denisova. Comparisons with sequences from contemporary humans from different parts of the world showed 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 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 same techniques that enabled these discoveries have been applied much more widely throughout the field of Paleogenomics, which continues to rewrite what we thought we knew about history and pre-history. The field has been advancing so quickly over the last decade that its hard to keep up with it. I’ve found the best introduction to be David Reich’s Who We Are and How We Got Here, though again the field is moving so fast that a 2018 book is already a bit out of date. Razib Khan is always writing about the latest updates at Unsupervized Learning. If you haven’t kept up with this stuff since school, this post and diagram give a quick introduction to how much our understanding of human origins has recently changed: