In a study published today in Science, Corinne Simonti from Vanderbilt University and her colleagues decided to take a different tack: They simultaneously looked at Neanderthal DNA across the entire genome and looked for associations with more than 1,600 traits and diseases. It was an unprecedentedly broad and systematic approach, made possible through an unlikely source of information: electronic medical records.

Since 2007, Vanderbilt researchers have been coordinating an 12-institute initiative called eMERGE (short for Electronic Medical Records and Genomics), analyzing the DNA of 55,000 volunteers and comparing those sequences to the patients’ medical records. Those records are goldmines of untapped data about the participants’ phenotypes—the full collection of their traits, including things like height, weight, cholesterol levels, heart function, cancer risk, and depression symptoms. Rather than looking for genes that are related to specific traits or diseases, as many large genetics studies do, eMERGE allows researchers to look for genes related to, well, pretty much anything in those records.

“We realized that it would be relatively straightforward to identify Neanderthal DNA in all these patients and analyze their [records] for a large range of phenotypes, which could speak to all kinds of traits and effects,” says Tony Capra from Vanderbilt University, who led the new study.

And so they did. They started with 13,700 people from the eMERGE Network, and looked for associations between 135,000 Neanderthal genetic variants and 1,689 different traits. They then checked any links they found against a second group of 14,700 eMERGE volunteers. “It is an exciting study—the first systematic assessment of the phenotypic impact of Neanderthal ancestry,” says Sriram Sankararaman from Harvard Medical School, who led an earlier study on Neanderthal DNA.

Capra and his colleagues found significant associations between Neanderthal variants and a dozen phenotypes, including actinic kerastoses (patches of dry, scaly skin caused by sun exposure) and a hypercoagulable state (where blood clots form too readily in the body).

Neither of these connections were particularly surprising: “Neanderthals had been living in central Asia and Europe for several hundreds of thousands of years before modern humans, so they were better adapted to the local climate, pathogens, and diets,” Capra says. “Perhaps interbreeding gave them a heads-up on adaptations to these challenges.” For example, Neanderthal variants could have shaped the skin cells of our ancestors, allowing them to cope with varying levels of ultraviolet radiation in new parts of the world; perhaps that is why such variants affect the risk of actinic kerastoses today. Similarly, blood clots close wounds and physically trap invading microbes; by influencing clotting, Neanderthal variants could have helped early humans to cope with new diseases.