A genetic inheritance from the extinct Denisovans appears to have provided early humans with a significant survival advantage as they populated the Americas. Research published in the journal Science identifies a specific variant of the MUC19 gene, originating from Denisovans, which is notably prevalent among Indigenous American populations.
This Denisovan-derived MUC19 variant is associated with the production of mucin proteins, key components of mucus that protect tissues from pathogens and support immune responses. The study suggests this genetic adaptation was likely beneficial for early human migrants encountering new environments and potential pathogens in the Americas. The variant is found in approximately one in three individuals of Mexican ancestry, particularly within genomic regions linked to Indigenous American heritage, highlighting its importance.
The research also details the complex pathways of genetic introgression, indicating that Denisovans interbred with Neanderthals, who then passed this genetic material to modern humans. This represents the first documented instance of a Denisovan gene reaching humans via a Neanderthal intermediary, described metaphorically as an "Oreo-like gene sandwich" with Denisovan DNA enclosed within Neanderthal sequences.
The high prevalence of this Denisovan MUC19 variant in ancient and modern Indigenous American populations suggests it was favored by positive natural selection, conferring a survival or reproductive benefit. Scientists are investigating how this variant may have strengthened immune defenses against specific diseases encountered during migration into the Americas. This discovery underscores the profound impact of ancient interbreeding events on human adaptation and resilience, providing a significant influx of beneficial genetic variation.
Further research is ongoing to fully understand the precise functions of the Denisovan MUC19 variant and its specific contributions to the health and survival of early American populations. The findings emphasize the dynamic nature of human evolution, illustrating how interspecies genetic exchange has shaped humanity's ability to thrive in diverse environments.