Stories of evolution often have curious origins. Our own evolution has one such tale, and it involves mating with Neanderthals.
Our Homo sapiens ancestors left Africa some 100,000 years ago. As they entered Europe and Central Asia, they would have inevitably come across Homo neanderthalensis who had walked those grounds for more than 100,000 years before that. We know what happened next, because the evidence can be found in our genes.
Its seems that those who mated with Neanderthals were successful in adapting more quickly to their new environment. Today’s non-Africans carry as much as 6% Neanderthal DNA in their genome.
“You can adapt through mutations, but if you interbreed with the local population who are already there, you can get some of these adaptations for free,” Janet Kelso of the Max Planck Institute for Evolutionary Anthropology in Leipzig told the Guardian.
Two new studies published in the American Journal of Human Genetics reveal why we still carry some of those Neanderthal genes. The first study by Kelso’s team specifically looked for DNA in modern humans that belonged to Neanderthals and their close relatives, Denisovans. They found that three of the most common Neanderthal and Denisovan genes belonged to the immune system’s functioning.
The second study by a team at the Pasteur Institute chose a different route of study. They used DNA belonging to the immune system from participants in the 1,000 Genomes Project. Among other findings, their study also confirmed the first study’s results about the three genes belonging to Neanderthals and Denisovans. It is likely that these genes helped humans evolve to fight new microbial infections, which Neanderthals had already adapted to.
Those genes may not be of such great use today, however. A 2014 study by the genetics company 23andMe had shown that people with those three genes were particularly susceptible to asthma, hay fever, and other allergies.