The extraction of the most ancient human DNA to date from human remains in Europe has provided pivotal insights into the intertwined evolution of Homo sapiens and Neanderthals.
Archeologists unearthed thirteen fragments of bone in a cave in Ranis, Germany, which hold the genetic blueprints of six ancient individuals who lived around 45,000 years ago. Published findings in Nature reveal these early humans possessed Neanderthal genetic markers, suggesting that interbreeding between the species occurred approximately 1,500 years earlier than historical estimates.
These primeval genomes, sequenced from the early inhabitants, solidify theories that there was genetic intermixing between Homo sapiens and Neanderthals.
This premise was previously postulated following the sequencing of the first Neanderthal genome in 2010, which posited that early humans mated with Neanderthals in the Middle East as they migrated out of Africa. The assumption was that humans and Neanderthals, who had been residing in Eurasia for a quarter of a million years, intercrossed during this migratory period.
In unison with the discovery in Nature, a companion study published in Science scrutinized genetic material from both ancient humans as well as 275 modern humans to pinpoint the Neanderthal ancestry in contemporary human DNA.
Priya Moorjani, a senior author of the Science publication and an assistant professor at the University of California, Berkeley, pointed out during a news conference, “We shared more similarities than differences… Their genetic material was integrated over an extensive duration, indicating prolonged coexistence.”
The research has pegged the time frame of this interbreeding to be between 50,500 and 43,500 years ago, with the zenith occurring around 47,000 years ago.
The prolonged genetic exchange is thought to have lasted for about 7,000 years, ending shortly before Neanderthals vanished from the archeological record. Modern human genomes contain Neanderthal DNA, making up 1% to 3% of our genetic structure, bearing traits that were advantageous during the ice age, particularly in regards to immunity and metabolic processes.
The Science article indicates that the predominate share of modern humans outside of Africa carries Neanderthal genetics from this period, hinting at a prominent migratory wave from Africa that likely ended by 43,500 years ago.
Nonetheless, unanswered questions persist, such as why present-day East Asians have greater proportions of Neanderthal ancestry compared to Europeans, as well as the scarcity of Homo sapiens DNA in Neanderthal genomes from that era.
Evolutionary geneticist Tony Capra, a professor at the University of California, San Francisco, expresses how ancient genetic information is invaluable, remarking that these studies “furnish a potent perspective that enabled the authors to refine our comprehension of human migration and Neanderthal integration.”
The research has also unearthed “archaic deserts,” which are genomic regions that lack Neanderthal genetic input, presumably because of natural selection’s role in eliminating harmful gene variants potentially causing diseases or developmental issues in offspring. The X chromosome stands out as particularly barren, leading to the inference that the presence of Neanderthal DNA in these regions carried a significant survival detriment.
Interestingly, the individuals who dwelled in the Ranis cave, as well as a related female found about 230 kilometers away in the Czech Republic, belong to an initial population that ultimately did not leave any living descendants.
Johannes Krause, a principal author of the Nature study and director at the Max Planck Institute for Evolutionary Anthropology, surmises, “Other groups of archaic humans also met their demise around 40,000 years ago, just as Neanderthals eventually did,” signifying a rich and intricate prehistoric narrative that reminds us Homo sapiens may not be the sole cause for the Neanderthals’ extinction.
