Hay fever? You can blame the Neanderthals for that
DNA from interbreeding with ancient neighbours linked to bacterial resistance, allergies
If you sneeze when flowers bloom in the spring and tear up in the presence of a cat, your Neanderthal DNA may be to blame.
About 2 per cent of the DNA in most people alive today came from trysts between ancient humans and their Neanderthal neighbours tens of thousands of years ago, recent studies have shown. Now, scientists are trying to determine what, if any, impact that Neanderthal genetic legacy has on our contemporary lives.
In a pair of papers published last week in the American Journal of Human Genetics, two research teams report that, in many people, the group of genes that govern the first line of defence against pathogens was probably inherited from Neanderthals.
These same genes appear to play a role in some people’s allergic reaction to things such as pollen and pet fur as well, the scientists said.
“It’s a bit speculative, but perhaps this is some kind of trade-off,” said Janet Kelso, a researcher at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, and senior author of one of the new studies. “Increased resistance to bacterial infection was advantageous, but may have resulted in some increased sensitivity to non-pathogenic allergens.”
About 50,000 years ago, the modern humans who left Africa encountered Neanderthal settlements somewhere in the Middle East, sci- entists believe. On some occasions, these meetings led to couplings whose legacy is apparent in the genomes of people with ancestors from Europe and Asia.
Not everyone with Neanderthal DNA inherited the same genes. But the immunity genes appear to be more popular than others. Among some Asian and European populations, the researchers found that these particular genes can be found in 50 per cent of people.
“That’s huge,” said Lluis QuintanaMurci, an evolutionary geneticist at the Pasteur Institute in Paris and senior author of the other study. “It came as a big surprise to us.”
The findings imply that these Neanderthal genes must have served our ancestors well if they are still present in our genome today, and especially at such high frequency, said Peter Parham, a professor of microbiology and immunology at Stanford School of Medicine.
“It suggests there was a benefit for the migrating modern human and the archaic human to get together,” said Parham, who wasn’t involved in the research. “What has survived is a hybridization of those populations.”
Both of the research groups report on a cluster of three genes — known collectively as TLR6-TLR1-TLR10 — that make up part of the body’s innate immune response to invading bacteria and viruses.
The innate immune response is different from the acquired immune response that we get through exposure to pathogens, either through vaccines or simply getting sick. Innate immunity kicks in first, and if it’s successful, it can destroy a pathogen in a few hours, before we even know we are sick.