Approximately 40,000 years ago, a remarkable transition unfolded across the Eurasian continent. Neanderthals, a species that had thrived for hundreds of millennia in the western regions of Eurasia, yielded ground to the encroaching Homo sapiens, who migrated from Africa. This monumental shift wasn’t instantaneous; instead, it marked a gradual coexistence of the two species, culminating in the integration of Neanderthal DNA into the genome of Homo sapiens.
Pioneering research conducted by scholars at the University of Geneva (UNIGE) has delved into the intricate distribution patterns of Neanderthal DNA within the genomes of Homo sapiens over the past 40,000 years. Through meticulous statistical analyses, these investigations have unveiled subtle variations across both temporal and geographical dimensions. Published in the prestigious journal Science Advances, this work provides invaluable insights into the shared history of these two ancient species.
Utilizing cutting-edge genome sequencing techniques and comparative analyses, researchers have established that interbreeding between Neanderthals and Homo sapiens was a common occurrence. These encounters bore fruit, leading to the preservation of approximately 2% of Neanderthal DNA in the genetic makeup of present-day Eurasian populations. However, intriguingly, this percentage exhibits slight disparities across different regions of Eurasia, with Asian populations boasting a marginally higher prevalence of Neanderthal DNA compared to their European counterparts.
One compelling hypothesis posits that the variation in Neanderthal DNA prevalence between Asian and European populations could be attributed to distinct effects of natural selection on genes of Neanderthal origin. However, Mathias Currat’s team, based at the UNIGE Faculty of Science, is exploring an alternative hypothesis.
Drawing upon previous research utilizing computer simulations, the team proposes that migratory flows might offer a more nuanced explanation for these differences. Specifically, when migrant populations hybridize with local populations, the proportion of local DNA tends to increase with distance from the point of departure of the migrant population.
Focusing primarily on European populations due to the abundance of archaeological excavations in the region, the researchers embarked on an extensive analysis. Leveraging a database comprising over 4,000 genomes from individuals spanning 40 millennia of Eurasian history, the study aimed to validate this migratory hypothesis.
The findings unveiled a fascinating narrative: following the dispersal of Homo sapiens from Africa, Paleolithic hunter-gatherers in Europe harbored a slightly higher proportion of Neanderthal DNA compared to their counterparts in Asia. This result aligns with paleontological evidence, as Neanderthal presence was predominantly concentrated in western Eurasia.
However, as the transition to the Neolithic era unfolded, marked by the advent of farming lifestyles, a pivotal shift occurred. Approximately 10,000 to 5,000 years ago, the proportion of Neanderthal DNA in European populations underwent a decline, dipping slightly below that observed in Asian populations. This decline coincided with the influx of Anatolian farmers into Europe, whose genetic makeup carried a lower proportion of Neanderthal DNA. Through intermingling with local populations, these incoming farmers further diluted the prevalence of Neanderthal DNA.
This comprehensive study underscores the power of integrating ancient genomic analyses with archaeological insights to unravel the complex tapestry of hybridized species’ histories. Moreover, it provides a foundational reference point for future investigations, offering a lens through which genetic anomalies—potentially harboring advantageous or disadvantageous effects—can be discerned with greater clarity.
Source: University of Geneva