Interbreeding with Neanderthals in Europe thousands of years ago left humans with gene variations that have increased our ability to ward off infection, two new studies suggest.
This inheritance from Neanderthals, however, may have also left some people more prone to allergies, the findings showed.
"We found that interbreeding with archaic humans - the Neanderthals and Denisovans - has influenced the genetic diversity in present-day genomes at three innate immunity genes belonging to the human Toll-like-receptor (TLR gene) family," said one of the researchers Janet Kelso from Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.
"This highlights how important introgression events (the movement of genes across species) may have been in the evolution of the innate immunity system in humans," Lluis Quintana-Murci from National Centre for Scientific Research (CNRS) in Paris, France, added.
The researchers set out to explore the evolution of the innate immune system over time.
Their interest was in understanding the functional importance of genes inherited from archaic humans more broadly.
They screened present-day human genomes for evidence of extended regions with high similarity to the Neanderthal and Denisovan genomes, then examined the prevalence of those regions in people from around the world.
Those analyses led them to the same TLR genes that are essential for eliciting inflammatory and anti-microbial responses and for activating an adaptive immune response.
Two of those gene variants are most similar to the Neanderthal genome, whereas the third is most similar to the Denisovan genome, the study showed.
"What has emerged from our study as well as from other work on introgression is that interbreeding with archaic humans does indeed have functional implications for modern humans, and that the most obvious consequences have been in shaping our adaptation to our environment - improving how we resist pathogens and metabolize novel foods," Kelso said.
Both the studies appeared in the American Journal of Human Genetics.
