The origin of Homo sapiens and the evolutionary processes that led them to present-day beings has always been a topic of intrigue and controversy. Though the evidence obtained are still not enough for a complete run-through of the history of human evolution, all that has been revealed after extensive paleontological and molecular research has enlightened just as much, as how we came into existence.
How did the Homo sapiens come into being?
The evidence unearthed by researchers dates the first appearance of primates 55-65 million years ago. With the appearance of the genus Homo about 3 million years ago, evolutionary processes led to the emergence of Homo erectus. They survived longer than the other hominin species and were the first known hominin to migrate out of Africa. Homo erectus possessed much of the modern human body proportions but with relatively long legs and shorter arms. This could have possibly indicated the first transition from arboreal to land-living beings. Homo sapiens are known to have first appeared in Africa; approximately 300,000 years ago; their migration from thereon to the Middle East and Eurasia saw their expansion. Our closest known relatives are known to be the Homo neanderthalensis– the Neanderthals- who evolved from the Homo erectus and were hominins much similar to the present-day humans, but much shorter, stockier and adapted to cold environments. They developed outside Africa and populated regions of Eurasia where they co-existed with Homo sapiens for many years before they eventually went extinct. Armed with all of these facts, scientists probed about the nature of interactions between us and our relatives- the Neanderthals, but to no avail because this required the study of both ancient and present-day human genomes by obtaining pure DNA samples.
Until Svante Pääbo accomplished this seemingly challenging feat.
Svante Pääbo, a Swedish geneticist, is now the Nobel prize winner for Physiology or Medicine for the year 2022 and the founder of Paleogenetics- the study of ancient DNA obtained from fossils- due to his discoveries concerning ‘the genomes of extinct hominins and human evolution.’
DNA can become chemically altered and fragmented with time, or get contaminated with microbial DNA and such, so the extraction of pure hominin DNA was itself challenging. Through extensive technical developments for better retrieving, sequencing and analyzing ancient DNA, Pääbo succeeded in analyzing the DNA of archaic specimens and discovered the links between modern and ancient hominins. He was able to obtain the undamaged and uncontaminated genome sequence of the Neanderthals and what was more, he discovered another, previously unknown, extinct hominin named Denisova from genomic data he retrieved from a small finger bone specimen!
Pääbo succeeded in publishing the first Neanderthal genome sequence in 2010. He found that gene transfer had occurred between the now-extinct relatives and Homo sapiens and that traces of their DNA remained in present human genomes. At the time when the Homo sapiens migrated out of Africa, the Neanderthals inhabited Western Eurasia while Denisovans populated the eastern regions of Eurasia. Thus at some point in history, Homo sapiens, Neanderthals and Denisovans co-existed in parts of Europe and Asia, they inter-bred, causing genes to mix and flow among them. This was proved when deeper delving showed that there were Neanderthal genes in humans that affected how our immune systems reacted to different types of infections.
Pääbo revealed genetic differences between living humans and the extinct hominins and the evolution of man from their extinct relatives, thus identifying features unique to present-day humans and adding valuable evidence and new discoveries to complete most of what was unknown about human evolution. With his major breakthroughs and founding of the new scientific discipline- Paleogenetics, it is certain that Pääbo has just opened the doors for many more budding scientists and novel research projects that are yet to come, to decode this whole mystery as to how we originated and came to be who we are today.
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