A new genetic analysis has revealed how the DNA of an extinct species has infiltrated the bloodline of modern Homo sapiens.
The research, led by population geneticist Priya Moorjani from the University of California, Berkeley, indicates that Neanderthal DNA in modern Homo sapiens comes from a unique and prolonged mixing period that occurred approximately 47,000 years ago.
Exhibition at Bacho Kiro Cave near Dryanovo, Bulgaria, which contains the remains of some Homo sapiens hybrids with Neanderthals aged 35,000-45,000 years – (Photo: SCIENCE/ANCIENT ORIGINS)
Homo sapiens – modern humans – are us, while Neanderthals represent a different species within the genus Homo, having diverged from a common ancestor at least 500,000 years ago.
As several previous studies have suggested, during the migration from Africa and the spread into Europe and Asia, our Homo sapiens ancestors encountered various other human species.
Among these encounters, interbreeding occurred with at least two species: Neanderthals and Denisovans.
However, the specifics of how this happened remain a mystery. All evidence of this interbreeding so far has predominantly been indirect evidence – for instance, about 2% of Neanderthal DNA is clearly present in the genomes of modern humans.
According to a summary of the study published in the journal Science, detailed sequencing of 59 ancient Homo sapiens genomes has helped American scientists trace back to that enigmatic period of coexistence.
The oldest DNA samples included remains from the Ust’-Ishim man in western Siberia (45,000 years old), the Zlatý kůň woman in the Czech Republic (45,000 years old), individuals from the Bacho Kiro Cave in Bulgaria (35,000-45,000 years old), and the Peștera cu Oase cave in Romania (40,000 years old).
Next, they identified the regions of Neanderthal DNA within these ancient Homo sapiens genomes and in the genomes of 275 modern Homo sapiens worldwide.
A computer software model tracked the evolution of Neanderthal genes over time, estimating how many generations would be needed for this hybrid genome to become as sophisticated as it is today.
The figure of 47,000 years was established from that point, alongside evidence showing that interbreeding between the two species occurred continuously over approximately 6,000-7,000 years.
This study not only provides crucial insights into the evolutionary and migratory processes of humanity but also confirms that modern humans have inherited certain genes from Neanderthals.
These genes are associated with skin pigmentation, immune responses, metabolism, and various diseases. Understanding them is significant for medicine and could lead to new treatment methods.
