It turns out that Neanderthal genes have a more significant role in modern human genetics than had been previously thought.
Researchers have known for a few years that around 2% of the DNA in most modern humans resulted from children born between early modern humans and their Neanderthal neighbors in the Middle East and Europe. It is thought that Neanderthal populations and Cro-Magnon human populations co-existed for several thousand years some 40 or 50 millennia ago.
Scientists have taken their research to the next step, and are now figuring out the impact that Neanderthal genetic legacy has on the lives of humans today. Two papers published January 7th in the American Journal of Human Genetics report that a set of genes that control the first line of defense against pathogens in the large majority of people today was very likely inherited from Neanderthals.
Moreover, the studies showed that these Neanderthal control genes also play a key role in the allergies many people suffer when they are exposed to pollen, pet fur and so forth.
More on Neanderthal genes in modern humans
Based on the data from the new studies, not everyone with Neanderthal DNA inherited all the same genes. That said, the pathogen immunity/allergies genes appear to have been positively selected fr over time. In fact, in some Asian and European populations, the research found these Neanderthal genes in close to 50% of the total population.
“That’s huge,” commented Lluis Quintana-Murci, an evolutionary geneticist at the Pasteur Institute in Paris and lead author of one of the studies. “It came as a big surprise to us.”
The data suggests that these Neanderthal genes served our ancestors well as they are still found in the genome of modern humans today, especially showing up at such a high frequency, noted Peter Parham, a professor of microbiology and immunology at Stanford (not involved in either study). He went on to explain that if the DNA wasn’t evolutionarily valuable, it would have been gradually eradicated from the human gene pool.
“It suggests there was a benefit for the migrating modern human and the archaic human to get together,” Parham elaborated. “What has survived is a hybridization of those populations.”
Moreover, give that infectious diseases have killed billions throughout human history, it only makes sense that genes offering immunity to pathogens would spread to throughout the population via natural selection.
Of interest, both of the research groups studied a cluster of three genes (known collectively as TLR6-TLR1-TLR10) that control much of the body’s innate immune response to bacteria and viruses.
Keep in mind that the innate immune response is not the same as the acquired immune response humans experience with exposure to pathogens, through vaccines or by getting sick. The body’s innate immunity is the first line of defense, and if strong enough, it can neutralize a pathogen in a few hours, and there are never any symptoms of the disease.
In her paper, Quintana-Murci emphasized that this innate immune response is so useful that it has become a strong site of positive selection over time.
Curiously, although the two research groups reached to the same conclusion, the teams were actually examining very different topics when the research first kicked off.