Denisovan legacy: Adaptive Significance of Archaic DNA in Papua New Guinea populations

In a new study, researchers have found differences in Denisovan DNA in the genomes of two distinct populations in Papua New Guinea - differences that might have contributed to adaptation to diverse environmental challenges. 

Denisovans are genetically a sister group to Neandertals. Like Neandertals, Denisovans interbred with modern humans, and their DNA still persists in some populations today. However, while Neandertal DNA is present in all non-African populations, Denisovan DNA is primarily found in populations in Oceania. Our understanding of Denisovans is limited compared to Neandertals due to the sparse fossil record, leaving significant gaps in our knowledge about their original habitat and physiology. Studying the phenotypic effects of Denisovan DNA in people today might therefore provide an inroad to learning more about this archaic group.

In present-day populations, Papua New Guineans (PNG) carry some of the highest levels of Denisovan DNA. A team led by researchers from the University of Tartu and the University of Toulouse, have analysed the genomes of 54 highlanders living at elevations of 2,300-2,700 metres on Mt. Wilhelm, and 74 lowlanders from Daru Island, living at around 100 metres above sea level. By examining differences in Denisovan DNA between these two populations from distinct environments, this study’s goal was to investigate the role of this archaic DNA in facilitating adaptive processes.

The study found that PNG highlanders carry higher levels of Denisovan DNA compared to their lowland counterparts. Notably, Denisovan DNA in highlanders is predominantly found in genomic regions linked to brain development while in lowlanders it was more associated with immune response genes.

“These findings are significant as they suggest that Denisovan DNA has contributed to adaptive traits in these populations, potentially offering insights into how Denisovans themselves may have adapted to similar environments in the past,” said Michael Dannemann, an associate professor at the University of Tartu and lead author of this study.

The researchers propose that the distribution of Denisovan DNA in these regions is not random but rather a signature of past adaptive processes. For highlanders, the Denisovan genetic variants linked to brain development could have provided advantages crucial for high-altitude living conditions. Conversely, for lowlanders, the Denisovan DNA associated with immune response might have been advantageous in their tropical environment, which presents a different set of pathogenic challenges.

This study provides valuable insights into the functional roles of Denisovan DNA, highlighting its contribution to the unique adaptations of Papua New Guinean populations. Moreover, it highlights the broader significance of archaic human admixture in shaping the evolutionary history of modern human populations.
 

DOI link