KELLY MCEVERS, HOST:
OK. Bear with me on this one. If you have hay fever or allergies, you might be able to blame a Neanderthal.
That is actually the conclusion of new research that came out today in The American Journal Of Human Genetics. NPR health correspondent Rob Stein reports.
ROB STEIN, BYLINE: Neanderthals got a bad rap for a long time. We humans thought they were dumb, brutish creatures but then scientists realized we had a lot more in common than anyone thought. In fact, Janet Kelso of the Marx Planck Institute in Germany says a lot of us have Neanderthal DNA scattered throughout our genes.
JANET KELSO: When modern humans were coming out of Africa, they met the Neanderthals who were living at that time in Europe and western Asia, interbred with them and carried with them some of the Neanderthal DNA as they migrated out into wider parts of the continent.
STEIN: So scientists have been trying to figure out what our Neanderthal DNA may be doing. Kelso and her colleagues and a second team of scientists in France examined the DNA for more than 2,000 people from around the world, hunting for genes from Neanderthals and another extinct species that lived at the same time known as Denisovans.
KELSO: And what we found was a set of three genes and they're really responsible for what we call innate immunity. This is our very early immune response. When the body detects that there is some foreign substance in the body, these are the guys that react immediately and it kind of calls in the big guns.
STEIN: ...To fight off whatever virus, bacteria or other invader threatens us. And it looks like these three genes helped early humans survive new diseases that attacked them as they migrated around the world.
KELSO: Perhaps it's not surprising, right? Neanderthals are living in Europe and western Asia for 200,000 years before modern humans arrive on the scene. And that means that they'd had time to adapt to the local environment - the pathogens, the climate. And when humans come in and breed with them, the things that we take away and keep are those that allow us to do the same thing - to adapt quickly and rapidly to local pathogens.
STEIN: But it turns out there's a downside to this for people today.
KELSO: This is a trade-off of sorts. So what you have is - you have an increased reactivity to potential pathogens, but you also have, as a kind of consequence of that, an increased reactivity to things that are not pathogenic, things like pollen and pet hair. So I suppose that some of us can then blame Neanderthals for our susceptibility to common allergies like a hay fever.
STEIN: Now, this isn't the first time scientists have discovered that Neanderthal genes still play a role in our lives. Believe it or not, Neanderthal genes help shape our skin and our hair. And Josh Akey of the University of Washington says this is all probably just for starters.
JOSH AKEY: I think this is really just the tip of the iceberg about how mating with Neanderthals influences all sorts of traits today - things like disease susceptibility and many other characteristics of humans.
STEIN: Akey says he's found more clues about how our Neanderthal ancestors are still with us and plans to report the details about that soon.
Rob Stein, NPR News.
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