NEANDERTHALS AND HUMANS | Facts and Details
In a recent revelation that challenges previous assumptions, a comparison of the genomes of a Neanderthal who resided in Siberia 120,000 years ago and modern humans in sub-Saharan Africa provides fascinating insights into the migratory and interbreeding history of both species.
It was conventionally believed that Neanderthals and Homo sapiens, or modern humans, met approximately 75,000 years ago. However, a groundbreaking new study, published in the journal Current Biology on October 13, proposes that Neanderthals and anatomically modern humans initiated their interbreeding journey approximately 250,000 years ago.
The earlier belief, based on a 2016 genetic analysis in the journal Nature, suggested that the interbreeding of Neanderthals and Homo sapiens took place around 75,000 years ago. However, this recent analysis challenges that notion. It asserts that a group of Homo sapiens originating from Africa interbred with Neanderthals in Eurasia around a quarter of a million years ago.
Although this group of humans eventually vanished, their genetic legacy remains within the DNA of Neanderthals descended from this ancient interbreeding event. Surprisingly, approximately 6% of the genome of a Neanderthal found in Siberia is composed of human DNA. Additionally, certain sub-Saharan human populations also carry traces of Neanderthal DNA, which they inherited when groups of humans, interbred with Neanderthals, migrated back to Africa.
“The enhanced understanding derived from this research will enable us to annotate Neanderthal DNA in modern human genomes, as well as the reverse process, with greater accuracy,” said Michael Dannemann, an associate professor of evolutionary and population genomics at the University of Tartu in Estonia, who was not involved in the research.
This newfound knowledge is expected to help scientists predict how interbreeding events influenced the physical attributes of both groups, shedding light on the migration patterns and interactions between modern humans and Neanderthals.
In 2020, the idea that most modern human-Neanderthal interbreeding happened in Eurasia faced challenges from a study in the journal Cell. This study uncovered Neanderthal DNA in human genomes in sub-Saharan Africa. Nevertheless, the origin of this Neanderthal DNA remained a mystery, and the analysis was limited to populations primarily of Niger-Congo-related ancestry.
In this recent study, the researchers compared the genome of a 122,000-year-old “Altai Neanderthal” from Siberia with that of 180 individuals from 12 diverse modern sub-Saharan African populations. They developed a sophisticated statistical tool to unravel the origins of the Neanderthal DNA found in the modern human genome.
This statistical analysis focused on genes shared by both humans and Neanderthals, attempting to discern whether certain alleles or genetic variants appeared to be of Neanderthal origin but had entered the modern human genome or vice versa.
The results showed that all the sub-Saharan genomes examined contained Neanderthal DNA, primarily derived from this 250,000-year-old interbreeding event. Some sub-Saharan populations displayed Neanderthal DNA in up to 1.5% of their genomes, which they inherited from humans who had returned to Africa after interbreeding with Neanderthals.
Moreover, the researchers found that the majority of human DNA in the Neanderthal genome existed in non-coding regions, indicating that human genes had been selected against during Neanderthal evolution. Conversely, the same region was devoid of Neanderthal DNA in the human genomes.
This suggests that neither species is inherently superior to the other; they simply evolved differently to suit their respective genetic needs. It underscores the idea that Neanderthals and modern humans represent two distinct species with distinct genetic profiles and evolutionary trajectories.
The authors of this study hope that their findings will pave the way for answers to other questions about human evolution. As Sarah Tishkoff, senior study author and professor in genetics and biology at the University of Pennsylvania, said, “It’d be really cool to learn more about the genome of that population that existed 250,000 years ago and compare it to the genomes of modern humans. Maybe that’ll tell us something interesting about human evolutionary history or adaptation.”
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