A recent genetic study suggests that Neanderthals predominantly inherited modern human DNA from the females in their lineage due to mate selection differences between Neanderthal males and females. Researchers from the University of Pennsylvania reached this conclusion by examining the distribution of anatomically modern human (AMH) and Neanderthal DNA in the X chromosomes of Neanderthals. This study, published in the journal Science, sheds light not only on Neanderthal biology but also on the social behavior of ancient populations.
The interaction between modern humans, originating from Africa, and Neanderthals in Europe and Asia led to interbreeding, resulting in the presence of Neanderthal DNA in all humans with non-sub-Saharan African ancestry. The genetic exchange was not uniform across all genes and chromosomes.
The researchers focused on the X chromosome, which is distinct because men possess only one, unlike other chromosomes that come in pairs. By comparing the X chromosomes of three ancient Neanderthal women with those of 73 modern human women from sub-Saharan Africa, the study revealed significantly higher levels of human DNA in the Neanderthal X chromosomes compared to their autosomes.
Possible explanations for this phenomenon include the superior functionality of human genes on the X chromosome in Neanderthals, unequal mating patterns favoring human ancestry in females, and the unique inheritance of X chromosomes from mothers to all offspring. This unequal genetic distribution suggests a preference for specific mate pairings that influenced the genetic makeup of Neanderthals.
The study authors proposed that multiple factors, such as mate preferences, migration patterns, and natural selection, contributed to the observed biases in Neanderthal X chromosomes. These findings align with previous research indicating potential reproductive challenges among Neanderthal-human hybrids due to genetic incompatibilities, influencing mating behaviors and outcomes.
The complexity of Neanderthal-human interactions and the genetic legacy left by these ancient populations highlight the intricate interplay between biology, social dynamics, and evolutionary processes shaping our genetic heritage today.