Nobel Prize Medicine 2022 announced. Here’s why Svante Pääbo’s work is remarkable
The Nobel Assembly at Karolinska Institute announced the 2022 Nobel Prize for Physiology or Medicine today and has recognized the pioneering work of Svante Pääbo, who, not only cracked the genetic code of our close relatives, the Neanderthals, but also found a whole new relative species in the Denisovans.
Humanity has been interested in understanding our origins and knowing more about those who came before us. Through the fields of archeology and paleontology, scientists have been attempting to satisfy this curiosity.
We now know that the modern human or Homo sapiens first appeared in Africa 300,000 years ago. Neanderthals, another hominin - human-like tribe, had developed outside Africa around 400,000 years ago and populated areas of Europe and Asia. About 70,000 years ago, modern humans migrated from Africa to the Middle East, from where they migrated to other parts of the world. During this time, they also came in contact with Neanderthals and possibly coexisted with them until the latter went extinct about 30,000 years ago.
In the 1990s, a new era was shaping up in medicine, where scientists began looking into the human genetic code, and the human genome project was completed. Pääbo wanted to use these tools to peek into the origins of human evolution and to study the DNA and genetic code of the Neanderthals to understand if they were genetically different.
The fragility of DNA
Pääbo soon found out that studying Neanderthals would be difficult since the DNA in Neanderthal samples degraded into short fragments and could not be studied using the same techniques. So, he began developing techniques that could be used instead.
While working at the University of Munich, Pääbo turned his attention to mitochondria, organelles that provide energy to the cell but also are equipped with their own DNA sequence. When compared to DNA in the nucleus of the cell, mitochondrial DNA is much smaller and contains less information. However, the abundance of mitochondra in the cell means that chances of success increase manifold.
Pääbo's methods bore fruit when he sequenced mitochondrial DNA from a 40,000 year-old piece of bone and we had the first evidence that Neanderthals were genetically different from modern humans. He was then offered a chance to establish a Max Plack Insitute in Germany, where he stepped up his research efforts to be able to sequence the nuclear genome of Neanderthals. In 2010, Pääbo and his research team published the first Neanderthal genome sequence. This helped us understand that the modern humans and Neanderthals had a common ancestor that lived around 800,000 years ago.
Pääbo and his colleagues also found evidence of Neanderthal DNA in modern humans, demonstrating that the two groups interbred and coexisted for thousands of years before Neanderthals went extinct.
Pääbo's moment of glory probably came when a 40,000-year-old finger bone was found in a cave in southern Siberia and when called upon to sequence its DNA, Pääbo and his team found that it was unique in every aspect, nothing like the DNA of Neanderthal or of modern humans. The researchers had found a previously unknown hominin, which was then dubbed Denisova, after the location of the cave.
Interestingly, modern humans in South East Asia show traces of Denisova DNA, demonstrating that these two groups had interacted in history. The gene EPAS1, found in Tibetans and gives a survival advantage at high altitudes, has a Denisovan version as well.
Apart from bringing to light the interactions of modern humans on their way out of Africa, Pääbo's work also provides information on important genetic differences with our closest relatives and what makes us uniquely human.
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