Neanderthals Interbreeding With Denisovans Helped Modern Immune Systems

Many people have Neanderthal genes in their DNA that predispose them to allergies, two studies published Thursday have found.

Interbreeding was a very smart move for early modern humans moving to Eurasia from Africa, UPI reports, because such a small population would have very little genetic variation. On some occasions, these meetings led to couplings whose legacy is apparent in the genomes of people with ancestors from Europe and Asia. However, the researchers found that in white blood cells, the Neanderthal and Denisovan TLRs are more highly expressed than the non-borrowed human TLR clusters.

According to Kelso and fellow researchers, it is still unclear whether the genes still protect people from pathogens today.

Interestingly, innate immunity genes present a higher average probability of Neanderthal ancestry than the rest of the coding genome. “It came as a big surprise to us”.

A new research has suggested that humans should thank their Neanderthal ancestors not only for giving the disease-fighting genes but also for their allergies. He went on to explain that if the DNA wasn’t evolutionarily valuable, it would have been gradually eradicated from the human gene pool.

Researchers found large numbers of people carry genes for Toll-like receptors, which play an important role in the immune system, that have been inherited from Neanderthals.

Because this innate immune response is so useful, it has been a strong site of positive selection over time, Quintana-Murci said.

The research comes from teams at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, and the Pasteur Institute.

Quintana-Murci’s group is trying to understand how microscopic pathogens have influenced the human genome as our species has evolved. Two of those gene variants are most similar to the Neanderthal genome, whereas the third is most similar to the Denisovan genome. Quintana-Murci and his colleagues chose to do a broad survey of innate immune genes and their variability among present-day humans around the world, using sequence data gathered through the 1,000 Genomes Project.

The team calculated the percentage of Neanderthal DNA in innate immunity genes as well as in other genes.

Finally, they estimated the timing of changes in innate immunity and the extent to which variation in those genes were passed down from Neanderthals.

“What has emerged from our study as well as from other work … 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.

What worked way back then may not be an asset in today’s environment. Among the three immune system genes that stood out, two closely matched Neanderthal DNA.

Interbreeding with Neanderthals could be responsible for allergies on modern humans.

“You’re able to take from a population that’s well-adapted in their immunity”, Kelso said. “This is perhaps not completely surprising”. Neanderthals were living in Europe and Western Asia for 200,000 years before modern humans arrived on the scene.

This has helped to confirm theories by anthropologists that our own species – Homo sapiens – interbred with these rival species as they spread out of Africa from around 60,000 years ago.