Ancient Denisovan DNA continues to shape human immunity today

Researchers from Yale University conducted a thorough analysis of the genomes of Near Oceanian populations that reveals how DNA inherited from the Denisovans, an extinct human group, remains active in present-day individuals. This work helps fill important gaps in genetic studies, which have traditionally focused more on populations of European descent.

By sequencing the genomes of 177 individuals from 12 distinct populations in regions such as Papua New Guinea, the Bismarck Archipelago, and the Solomon Islands, the scientists combined this data with over a thousand previously published genomes. In this way, they managed to reconstruct part of the history of the first Pacific settlers, who arrived at least 45,000 years ago.

One of the most relevant findings is that the ancestors of these populations interbred with at least three different groups of Denisovans. This left genetic variants that persist to this day and are not just inactive remnants of the past.

These variants actively influence gene regulation, which represents a significant advance in understanding how evolution shaped our biology.

Variants that strengthen defenses

Using an advanced technique called massively parallel reporter assay, the team identified over 3,100 variants that modify gene expression. Many of them are linked to the interferon gamma signaling pathway, crucial for the immune response against infections.

"The DNA of extinct hominids like Denisovans and Neanderthals helped humans adapt to the different environments they encountered while migrating," explained one of the lead authors. In Near Oceania, these variants would have strengthened immunity against local viruses and bacteria.

The study highlights that pathogens represented one of the strongest selective pressures throughout human evolution. Therefore, the genetic contributions of Denisovans appear to have been adaptive for survival in that region.

In addition to immunity, there is evidence that Denisovan DNA influences skeletal development, particularly in a gene called TRPS1. This same gene showed positive selection in other distant populations, such as hunter-gatherers in African rainforests and highland inhabitants in Ecuador.