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Ancient Encounters: Unraveling a Mysterious Human Lineage Through Neanderthal Genomes
Varied African genetic profiles unveil ancient natural selection acting upon interbreeding between early modern humans and Neanderthals.
In the intricate tapestry of human evolution, a recent revelation challenges our understanding of ancient migrations and interbreeding. Researchers, delving deep into the Neanderthal genome, have unearthed traces of an enigmatic human lineage that once traversed the landscapes of Eurasia. They published their findings in Current Biology1. This discovery not only extends the timeline of Homo sapiens' presence in Eurasia but also sheds light on complex intermingling between different human species.
As modern humans migrated into Eurasia over 70,000 years ago, they encountered Neanderthals, close relatives who had diverged from our common ancestor nearly half a million years ago. Interbreeding between these hominin species has long been documented, leaving traces of Neanderthal DNA in the genomes of many present-day humans. However, a recent study has unveiled an intriguing twist—a genetic signature indicating an encounter between Neanderthals and a previously unknown lineage of early Homo sapiens.
According to this study, a group of Homo sapiens, genetically akin to us, ventured into Eurasia approximately 250,000 to 270,000 years ago. These early modern humans were the cousins of present-day humanity, sharing remarkable similarities with us. Their genetic legacy, once thought lost in the annals of time, has resurfaced through meticulous genomic analysis, revealing unexpected chapters of ancient human migration and interaction.
The clues to this ancient encounter were found within the Neanderthal genome itself. Through a methodical analysis of Neanderthal-homologous regions (NHRs) in diverse African populations, researchers uncovered a fascinating pattern. Neanderthal-like DNA, previously associated predominantly with Eurasian ancestry, was discovered in African populations. However, this genetic influx was not solely due to Neanderthal interbreeding in Africa. Instead, it primarily originated from the ancient Homo sapiens lineage that had migrated from Africa to Eurasia.
This ancient encounter left a lasting legacy in both Neanderthal and modern human genomes. Up to 6 percent of the Neanderthal genome, the researchers found, was inherited from these early Homo sapiens. Remarkably, this genetic exchange influenced not only the Neanderthals but also certain human populations migrating back to Africa from Eurasia, creating a complex interwoven web of genetic diversity.
Despite interbreeding, Neanderthals and modern humans had undergone substantial evolutionary divergence during their 500,000 years of separation. The study emphasizes that, although interbreeding occurred readily, significant differences had emerged between the two species. The ongoing process of natural selection has gradually removed alleles inherited from each group, highlighting the intricate dynamics of genetic adaptation.
The discovery of this unknown human lineage buried within the Neanderthal genome illuminates a captivating chapter in our evolutionary saga. Through the lens of advanced genomic analysis, we witness the ancient footsteps of our early modern human relatives, their interactions with Neanderthals, and the intricate genetic dance that shaped our shared ancestry. As scientists continue to unveil the mysteries of our past, this discovery stands as a testament to the complexity of human evolution, urging us to reevaluate our notions of ancient migrations and the interconnections of our species across millennia.
Harris, D. N., Platt, A., Hansen, M. E. B., Fan, S., McQuillan, M. A., Nyambo, T., Mpoloka, S. W., Mokone, G. G., Belay, G., Fokunang, C., Njamnshi, A. K., & Tishkoff, S. A. (2023). Diverse African genomes reveal selection on ancient modern human introgressions in Neanderthals. Current Biology: CB. https://doi.org/10.1016/j.cub.2023.09.066