Scientists have found new evidence suggesting that a recently discovered ancient human group, known as the Denisovans, interbred with early humans and contributed to the genetic makeup of our species. This interbreeding is believed to have occurred multiple times, significantly influencing the course of human evolution.
In 2010, the first draft of the Neanderthal genome was released. Comparisons with contemporary human genomes revealed that Neanderthals and early humans had interbred. Shortly after, a genome extracted from a finger bone found in Siberia’s Denisova Cave led to the discovery of a new group of ancient humans, now called Denisovans, who also interbred with our ancestors.
“This discovery was a game-changer in our understanding of human evolution,” says Dr. Linda Ongaro, a postdoctoral researcher at Trinity College Dublin’s School of Genetics and Microbiology. Dr. Ongaro is the lead author of a comprehensive review article published in the prestigious journal, Nature Genetics.
“Many people think that human evolution was a straightforward process from a single ancestor, but the more we learn, the more we see that our history is full of instances of interbreeding with different hominins, like the Denisovans, that shaped us,” she explains.
While only a few Denisovan fossils have been found — a finger bone, a jawbone, teeth, and fragments of a skull — scientists have been able to identify Denisovan genes in modern human genomes. This has provided evidence of at least three separate instances of interbreeding between Denisovans and modern humans.
The review article, co-authored by Dr. Ongaro and Prof. Emilia Huerta-Sanchez, presents evidence that suggests Denisovan populations were widespread and adapted to different environments. They could have ranged from Siberia and Southeast Asia to Oceania and South America.
The authors also highlight specific Denisovan genes that gave early humans advantages in adapting to various environments. “Among these is a gene that allows for better tolerance of low oxygen conditions, seen in Tibetan populations; several genes that boost immunity; and one that boosts metabolism, providing warmth in cold conditions, benefiting Inuit populations in the Arctic,” Dr. Ongaro shares.
Further research is required to tell a more comprehensive story of the Denisovans’ impact on modern humans. This includes detailed genetic analyses in understudied populations to uncover hidden traces of Denisovan ancestry, and integrating genetic data with archaeological findings, should more Denisovan fossils be discovered.
