Medicine Nobel goes to Svante Pääbo: What his research tells us about human evolution

Context–

The Nobel Prize 2022 for Medicine was awarded to Swedish academic Svante Pääbo“for his discoveries concerning the genomes of extinct hominins and human evolution.”
Through his pioneering research, Svante Pääbo has successfully sequenced the genome of the Neanderthal, an extinct relative of present-day humans.
He also made the sensational discovery of a previously unknown hominin, Denisova.
The Nobel Assembly said Svante Pääbo’s discoveries on evolution have helped “provide the basis for exploring what makes us uniquely human”.

His work, explained

Hominins refer to the now-extinct species of apes that are believed to be related to modern humans, as well as modern humans themselves.
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.

Relation between evolution and biology–

Svante Pääbo established an entirely new scientific discipline, called paleogenomics, that focuses on studying the DNA and genetic information of extinct hominins through reconstruction.
Archaic gene sequences from our extinct relatives influence the physiology of present-day humans.
An example of this linkage is when Pääbo extracted DNA from bone specimens from extinct hominins, from Neanderthal remains in the Denisova caves of Germany.
The bone contained exceptionally well-preserved DNA, which his team sequenced.
It was found that this 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 then given the name Denisova.
Comparisons with sequences from contemporary humans from different parts of the world showed that gene flow, or mixing of genetic information among a species, had also occurred between Denisova and Homo sapiens – the species of modern-day humans.
This relationship was first seen in populations in Melanesia (near Australia) and other parts of South East Asia, where individuals carry up to 6% Denisova DNA.
The Denisovan version of the gene EPAS1 confers an advantage for survival at high altitudes and is common among present-day Tibetans.

Challenges in carrying out such research–

With time DNA becomes chemically modified and degrades into short fragments.
The main issue is that only trace amounts of DNA are left after thousands of years, and exposure to the natural environment leads to contamination with DNA from bacteria and contemporary humans, making research complex.
Remarkably, when he managed to sequence a region of mitochondrial DNA from the 40,000-year-old Denisovan piece of bone, it marked the first time researchers had access to a sequence from an extinct relative.