The study looked specifically at health conditions, finding associations between Neanderthal DNA and conditions related to immune response, blood clotting, and depression by using electronic health records from more than 50,000 individuals. When humans migrated out of Africa they intermixed with Neanderthals perhaps 60,000 years ago, and so all non-Africans carry some remnant of Neanderthal DNA. Scientists believe that by mixing with Neanderthals, who lived and thrived in Europe and Asia for 100,000 years, modern humans got an evolutionary advantage as they migrated into those new environments.
A paper published earlier this year suggests that intermixing with Neanderthals conferred an advantageous immune response for populations that ultimately settled in Europe. Another study two years ago looked at how intermixing with another ancient human cousin, the Denisovan, may have conferred an evolutionary advantage for Tibetans to cope with high altitude through a variant in the EPAS1 gene that helps to prevent blood thickening. But some of those same traits inherited from Neanderthals – and presumably other ancient human cousins – that tens of thousands of years ago may have been advantageous, may not be beneficial in modern times when diet and lifestyle are so different.
“These variants sometimes protect against a disease,” said Svante Paabo the Max Planck Institute for Evolutionary Anthropology.
Interviewed for a story in Science Magazine about the findings Paabo added that some of the variants may “sometimes make people more susceptible to disease.”
Although the Vanderbilt study focuses just on health related traits, it illustrates the potential of looking at a broad grouping of phenotypes like those in the electronic medical records, with known Neanderthal variants. (23andMe reports to customers the number of Neanderthal variants they carry, how that compares with other customers, and traits those variants are associated with such as back hair and height.)
In an article in the Atlantic, Ed Yong points this out and notes that, instead of focusing on the associations with disease, attention around this study might be better focused on what those associations can tell us about the biology of certain conditions. For instance, the researchers found that Neanderthal DNA is associated with depression and certain mood disorders. Specifically, researchers speculate variants that helped Neanderthals adapt to lower sunlight exposure in northern latitudes, could have carried a higher risk for depression, which is influenced by sunlight exposure.