Recent studies have unveiled a detailed timeline of interactions between modern humans and Neanderthals, an extinct group of ancient humans that inhabited Eurasia. As modern humans migrated out of Africa tens of thousands of years ago, they encountered Neanderthals, leading to a genetic exchange that is evident in the DNA of nearly all non-African humans today.
Despite extensive research, the specifics regarding the timing and impact of these interactions remained unclear. Two significant studies published in the journals Science and Nature, conducted by researchers from the University of Rochester and the Max Planck Institute for Evolutionary Anthropology, have reconstructed the timeline of interbreeding and its evolutionary consequences. The findings indicate when and where these exchanges occurred and how Neanderthal genes contributed to human adaptation in new environments.
Benjamin Peter, an assistant professor at the University of Rochester, noted, "Our study provides the most detailed insights yet into how Neanderthal gene flow impacted human genomes." The divergence of Neanderthals and modern humans occurred approximately 500,000 years ago, with Neanderthals evolving in Eurasia and modern humans in Africa. Both groups exhibited complex behaviors, but Neanderthals developed distinct physical traits suited to their environment.
Modern humans began migrating out of Africa around 40,000 to 60,000 years ago, leading to interbreeding with Neanderthals. This gene flow resulted in most non-Africans carrying one to two percent Neanderthal DNA. However, the precise timing of this genetic exchange had been elusive.
The researchers analyzed over 300 genomes from ancient and modern humans over the past 50,000 years, identifying patterns of Neanderthal DNA. Their results revealed that the majority of Neanderthal DNA in modern humans originates from a single major period of gene flow approximately 47,000 years ago, lasting around 7,000 years. This suggests a singular extended interaction rather than multiple separate events.
Additionally, the study highlights that Neanderthal DNA is not uniformly distributed across the genome. Certain regions associated with traits like skin pigmentation and immune function show higher concentrations of Neanderthal DNA, indicating that some of these genetic variants provided immediate benefits for survival.
As researchers continue to gather genetic data, particularly from regions like the Middle East and South Asia where early human-Neanderthal interactions remain unclear, further insights into this pivotal moment in human history are anticipated.