Many people have Neanderthal genes in their DNA that predispose them to allergies, two studies published Thursday have found.
"So I suppose that some of us can blame Neanderthals for our susceptibility to common allergies, like hay fever," says Janet Kelso of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, who led one of the teams.
Scientists once thought of Neanderthals as brutish creatures who had little in common with modern humans. But as more evidence turned up, researchers realized Neanderthals were more sophisticated than previously thought and sometimes mated with early Homo sapiens.
"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," Kelso says.
So Kelso and her colleagues and a second team from the Pasteur Institute decided to search through human DNA collected by the 1,000 Genomes Project for genes from Neanderthals and a third kind of early human — the Denisovans — that may be involved in regulating immunity.
Both teams identified three genes from these two extinct groups that play a role today in controlling a part of the human immune system known as "innate immunity."
"When the body detects that there is some foreign substance in the body, these are the guys that react immediately," Kelso says. "It kind of calls in the big guns" by mobilizing key immune system cells to attack.
These genes would have helped enable early humans to survive new diseases encountered as they traveled throughout the world, Kelso says.
"It's not surprising, right?" Kelso says. "Neanderthals were living in Europe and western Asia for 200,000 years before modern humans arrived on the scene. And that means that they'd had time to adapt to the local environment," including pathogens.
And when humans arrived and bred with the Neanderthals, it makes sense that evolutionary pressures would make it more likely that these ancestors of modern humans retained genes that allowed them to "adapt quickly and rapidly to local pathogens," Kelso says.
But there appears to be a downside for people who still carry these particular genes today. The same bits of DNA make the immune system more likely to overreact to certain stimuli such as pollen and animal hair, and increase the risk of developing other sorts of allergies.
"This is a trade-off of sorts," Kelso says. It remains unclear whether those genes also are still protecting people from pathogens, she and other scientists say.
"That's sort of the $1 million question," says Lluis Qutintana-Murci, with the Pasteur Institute in Paris, who led the second research team. "What was good in the past may or may not be good for us today."
But it is clear that Neanderthal genes do more than just affect the immune system. Previous research found Neanderthal DNA seems to influence human hair and skin, for example.
"I think this is really just the tip of the iceberg about how mating with Neanderthals influences all sorts of traits today," says Josh Akey, a professor of genome sciences at the University of Washington who studies Neanderthal and human DNA.
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. Transcript provided by NPR, Copyright NPR.