Nobel Prize in Physiology or Medicine 2022
The 2022 Nobel Prize in Physiology or Medicine was awarded to Svante Pääbo by the Nobel Assembly at Karolinska Institutet. He was given the prestigious award for his discoveries regarding the genomes of extinct hominins and human evolution.
We have always been intrigued by our origins. Where do we actually come from? How are we connected to those who came before us? What is the difference between Homo Sapiens and other hominins? All such questions keep arising in our brain every now and then.
Through his instigating research Svante Pääbo accomplished something which many thought was never possible. He successfully performed the genome sequencing of Neanderthal, an extinct relative of modern-day humans.He also made the pathbreaking discovery of previously unknown hominin called Denisova. Pääbo found out that gene transfer had happened from these extinct hominins to Homo sapiens as a result of the migration out of Africa 70,000 years ago.The ancient flow of genes to present-day humans have great relevance, it determines how our immune system reacts to infections.
His discoveries made way for an entirely new scientific discipline called paleogenomics. They help us in exploring what makes us uniquely human, by disclosing genetic differences which distinguish living humans from extinct hominins.
Human evolution is studied with the help of paleontology and archeology. The question of our origin has kept humans guessing since ancient times. As per the research, Homo Sapiens (modern humans) first appeared in Africa around 300,000 years ago. Our closest known relatives are the Neanderthals. They developed outside Africa. The population grew in Europe and Western Asia from around 400,000 years until 30,000 years ago, at that point they went extinct. Groups of Homo Sapiens migrated from Africa to the Middle East about 70,000 years ago. From there they expanded to the rest of the world. In large parts of Eurasia, Homo sapiens and Neanderthals coexisted for tens of thousands of years. The entire human genome had been sequenced by the end of 1990s. Sequencing of genomic DNA recovered from Archaic specimens is essential for studying the relationship between modern-day humans and extinct Neanderthals.
Svante Pääbo along with Allan Wilson tried to develop methods to study DNA from Neanderthals for over several decades. He was recruited to the University of Munich as professor in 1990. He continued his research on archaic DNA. After constant efforts, he finally managed to sequence a region of mitochondrial DNA from a 40,000-year-old piece of bone. Finally we had access to a sequence from an extinct relative. It was found that Neanderthals were genetically different after comparisons with humans and chimpanzees.
Going ahead, Pääbo took up the big challenge of sequencing the Neanderthal nuclear genome. His research progressed at Max Planck Institute in Leipzig, Germany. He engaged several collaborators who were experts on population genetics and advanced sequence analyses. Pääbo achieved great success, he published the first Neanderthal genome sequence in the year 2010.
Pääbo and his team investigated the relationship between Neanderthals and modern humans from various parts of the world. Studies revealed that DNA sequences from Neanderthals were akin to sequences of modern humans originating from Europe or Asia than to modern humans originating from the African continent. This is a proof for the fact that Neanderthals and Homo Sapiens interbred during their millennia of coexistence. In short, in present day humans of European or Asian descent, at least 1 – 4 percent of the genome originates from the Neanderthals.
The sensational discovery
A 40,000-year-old fragment from a finger bone was discovered in the Denisova cave in the year 2008, in the southern part of Siberia. The DNA sequence was unique when compared to sequences from Neanderthals and modern-day humans. Pääbo had earlier discovered an unknown hominin which was called the ‘Denisova’. Comparisons with sequences from modern humans from various parts of the globe suggested that gene flow had also occurred between Denisova and Homo sapiens. It is in the populations of Melanesia and other parts of SouthEast Asia in which this relationship was first visible. Individuals in these parts of the world carry up to 6 percent Denisova DNA.
Pääbo’s discoveries served as a game-changer in the study of evolutionary history. When Homo sapiens were migrating out of Africa, two extinct hominin populations were inhabiting Eurasia. While Neanderthals lived in Western Eurasia, Denisovans were predominantly present in the eastern parts of the continent. Homosapiens during their expansion encountered and interbred with both Neanderthals and Denisovans.
Paleogenomics, an entirely new scientific discipline, was established by Svante Pääbo through his path breaking research. His team has already completed analyzing several additional genome sequences from extinct hominins. Pablo’s discoveries are used by the scientific community to better understand human evolution and migration. Latest sequence analysis indicates mixing of archaic hominins with Homo Sapiens in Africa. Due to accelerated degradation of archaic DNA in tropical climates, scientists have not yet been able to sequence genomes from extinct hominins in Africa.
Svante Pääbo’s discoveries show us that the physiology of modern-day humans are influenced by the archaic gene sequences from our extinct relatives. For example, the Densovian version of the gene EPAS1 gives present-day Tibetans an advantage for surviving at high altitude. Another major example are Neanderthal genes which affect our immune response to various types of infections.
Capacity to create complex cultures, advanced innovations and figurative art is unique to Homo Sapiens. They also have the ability to cross open water and spread to various parts of the planet. Over the years, they also made use of tools. Pääbo’s seminal work discovered the genetic differences between Homo Sapiens and our closest extinct relatives. Ongoing research focuses on implications of such differences trying to explain what makes us uniquely human.
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Answer) Svante Pääbo