On October 3, 2022, the Nobel Prize for Medicine was awarded to Swedish academic Svante Paabo, a geneticist of Estonian descent who specialises in the field of evolutionary genetics, for his discovery concerning the genomes of extinct hominins and human evolution. The discovery is of paramount importance in understanding human evolution. He has amplified and sequenced complicated ancient DNA because it is highly fragmented, and full of contamination from microbes like fungi and bacteria. His research has helped in furthering the recognition of evolutionary biology and palaeogenomics. (Palaeogenomics is a field of science based on the reconstruction and analysis of genomic information in extinct species).
About the Research
Acquiring genetic information of organisms that had gone extinct thousands of years ago could be a herculean task because of the complication in collecting their DNA. Though it is practicable to take out DNA samples from fossils and remains, it is complicated in comparison to getting it from organisms that inhabited Earth in more contemporary times. Paabo was appointed as a professor at the University of Munich in 1990 where he continued his research to study DNA from extinct human species. He studied mitochondrial DNA from Neanderthals. (Mitochondria, popularly called as the ‘powerhouse of the cell’, is an organelle inside the cell that has its own DNA.) Although the mitochondrial genome is small and only contains a fraction of the genetic information in the cell, it is present in thousands of copies. This increased the chance of its successful sequencing.
He successfully sequenced a part of mitochondrial DNA from a 40,000-year-old bone. A comparison of this with the contemporary humans and chimpanzees showed that Neanderthals were genetically distinct.
Paabo, as one of the founders of Palaeogenetics, and founding director of the Department of Genetics at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, published his first Neanderthal, a human species that went extinct around 30,000 years ago, genome sequence research paper in 2010, in which he had outlined his team’s analysis of 21 Neanderthal bones from Vindija Caves, in Croatia. Bone powder from these specimens was analysed and three bones were selected for further analysis. Nine DNA extracts were prepared from the three bones. The DNA and microbial contamination were factored in before continuing with the investigation.
Svante Paabo’s team experimented with five present-day human genomes from different regions—one San from Southern Africa, one Yoruba from West Africa, one Papua New Guinean, one Han Chinese, and one French from Western Europe. These genomes were sequenced and analysed against the Neanderthal genome derived from the experiment to put divergence in the DNA of the two into perspective. The researchers noted that the divergence of the Neanderthal genome to the human reference genome was greater than for any of the present-day human genomes that had been analysed. The Neanderthal genome allowed the researchers to identify the features that are unique to present day humans, relative to other hominins.
He has also discovered the existence of an unknown sub-species of the human family, which is known as the Denisovans, who lived around the same time as the Neanderthals. In 2008, Paabo’s team had sequenced the DNA from an ‘exceptionally well-preserved’ 40,000-year-old fragment from a finger bone, found in the Denisova cave, in Siberia. The DNA sequence turned out to be unique. It was different from all known sequences from Neanderthals and present-day humans. The previously-unknown hominin Denisova was, thus, discovered. This also proved that the Neanderthals and Denisovans had co-existed for about 20,000 years. According to his research, they not only had interacted with each other, but were inter-bred as well. In some populations of modern human beings, around one to three per cent of the genome has been found to originate from the Neanderthals.
The genetic differences between Homo sapiens and our closest extinct relatives were unknown until they were identified through Paabo’s seminal work. Intense ongoing research focuses on analysing the functional implications of these differences with the ultimate goal of explaining what makes us uniquely human.
Significance of the Research
Paabo’s research is an attempt to answer questions about human evolution. He also discovered Denisova, a previously unknown hominin. Hominins are extinct members of the human lineage. His research has led to the discovery that gene transfer had occurred from these now extinct hominins to (Homo sapiens, following the migration out of Africa around 70,000 years ago. Homo sapiens is characterised by the ability of innovation, figurative art, and the ability to cross open water and spread across the globe.) The ancient gene flow has significant physiological relevance for present-day humans. It remains to be seen if the interest in this field would result in better funding and more researchers. The research has led to the rise of a new scientific discipline, known as palaeogenomics (the study and analysis of genes of extinct organisms.)
Alfred Nobel, the Swedish chemist, engineer and industrialist, who invented dynamite, gave the largest share of his fortune to a series of six prizes (physics, chemistry, medicine, literature, peace, and economics) in his last will and testament, on November 27, 1895. They were split into multiple prizes, one of which was dedicated to “the person who shall have made the most important discovery within the domain of physiology or medicine”. Each prize consists of a medal, a personal diploma, and a cash award.
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