The winner of the 2022 Nobel Prize for Medicine and Physiology, Svante Pääbo, could take that Peruvian expression and say, to refer to the genetics of the modern human being, that “he who is not Denisovan is neanderthal”.
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Dr. Pääbo started working in the 1980s trying to recover DNA from Egyptian mummies. He published a study in 1985 that was severely criticized because what was reported as Egyptian DNA was actually material from the researchers, which had contaminated the sample.
Taking advantage of the nascent PCR (Polynerase Chain Reaction) technology that facilitated DNA and RNA sequencing, Dr. Pääbo went to Germany and began to investigate the genetics of the ancient human ancestors of today.
Although it is accepted that there must be many more, and that they are yet to be discovered, it is thought that there were at least eight species of hominids before ‘Homo sapiens’.
The ‘Homo habilis’ (handy man), discovered in 1960, evolved in Africa about two million years ago and became extinct on that continent about 1.5 million years ago. Homo erectus (upright man), discovered in 1891, probably evolved in Africa about two million years ago, rapidly expanded and spread across Eurasia, and is believed to have disappeared 143,000 years ago.
Homo neanderthalensis (Neanderthal), discovered in 1829, appeared in Eurasia about 200,000 years ago and became extinct there about 40,000 years ago. They are considered the cousins of modern human beings and it is thought that they knew how to control fire and developed primitive instruments of stone and bone. It is also believed that they developed some kind of primitive medicine and left works of art.
The Denisovans were discovered by Pääbo in 2010, from a segment of the little finger of a fossil found in present-day Russia. They probably lived throughout East Asia from around 200,000 years ago and disappeared around 50,000 years ago. The existence of the Denisovans has only been proven by genetic analysis, no fossils of this hominid have yet been found.
‘Homo floresiensis’ (the “hobbit”), found in 2003, lived on the Indonesian island of Flores between 100,000 and 50,000 years ago. ‘Homo naledi’ (star man), found in 2013, lived in South Africa and may have existed between 300,000 and 200,000 years ago. ‘Homo sapiens’ (wise man) are modern humans. The species is thought to have appeared in Africa about 200,000 years ago, left that continent at least 100,000 years ago, and spread to the rest of the world.
The meaning of Pääbo’s work
For a long time it was thought that these hominin species were branches of common ancestors and that they became extinct separately. That is to say, it was never thought that there could be times in which these species could coexist, meet, cohabit, have sexual relations and have children.
The pioneering work of Pääbo – who created paleogenetics – is to scientifically demonstrate that Neanderthals lived and interbred with ‘Homo sapiens’ and Denisovans for years in Europe and Asia.
In 2010, Dr. Pääbo published his study in which he describes, for the first time, the genome of a Neanderthal and the study that describes the genome of a Denisovan, discovered two years ago.
Once the genome of a Neanderthal was known, scientists were able to compare it with that of the current human being and came up with several surprises.
The first is that it is considered that the genome of the inhabitants of Europe and Asia has 2% to 4% of Neanderthal genes, which in recent studies have shown that they give modern humans interesting characteristics.
A study of Dr. Pääbo from 2020 finds that people with Neanderthal genetic segments – from 60,000 years ago – are more likely to suffer from more severe COVID-19. That part of the genome, which encompasses six genes on chromosome 3, is present in 63% of people in Bangladesh and 30% of South Asians. Instead, it is only in 8% of inhabitants of Europe and 4% in East Asia. Those genetic changes are almost completely absent in Africa.
The exact meaning of this finding is not known. It could be that this segment was left out for being harmful to the species.
A study published on September 9 in “Nature” finds that our brain differs from the Neanderthal in only one gene (TKTL1), which has been shown to allow the current brain to form more connections between neurons, which undoubtedly give a huge evolutionary advantage in the emotional and intellectual field.
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One of the biggest consequences of Dr. Pääbo’s findings is that they debunk racist and nationalist ideas that pure races exist. That, as shown in genetic studies, is simply impossible.
The current human being is the product of evolution and the interbreeding of numerous previous species, which for unknown reasons became progressively extinct after mixing their genes. Some 40,000 years ago, ours was the last surviving human species on earth, and we are certainly still evolving.
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The Nobel Prize for a coexistence in which nobody thought