Around 60,000 years ago, modern humans left Africa to begin exploring other continents. Along the way they met other early humans, such as Neanderthals, and the different species periodically bred together. Scientists have known this for a few years—there’s evidence in our DNA, of which 1.5 to 4 percent in modern Europeans is Neanderthal (it’s even higher in people from other parts of the world–people from East Asia have 20 percent more Neanderthal DNA). But scientists never knew if those bits of genetic code had a lasting effect on our health. After analyzing specific parts of DNA in 28,000 people, a team led by researchers at Vanderbilt University discovered correlations between Neanderthal DNA and 12 different health conditions, including depression and disorders of the skin and blood. The researchers published their work today in the journal Science.

The researchers identified 135,000 alleles, or variations in the genetic code, that some modern humans had inherited from Neanderthals. They then correlated the presence of those variations to more than 1,500 medical conditions listed in the patients’ electronic medical records.

Neanderthal DNA was correlated with a higher incidence of depression, addiction to tobacco, skin lesions caused by the sun, a slower metabolism, too much blood clotting, and a mutation connected to Parkinson’s disease.

Clearly, these genetic variations aren’t helping us be healthier these days. But that might not have always been the case. Back when humans and Neanderthals were roaming around Europe together, faster blood clotting would have been essential to quickly close open wounds to stave off infection. A slower metabolism would have been useful when food was more scarce or lower in calories than we have now.

The findings show how much can be gleaned from a huge dataset like the one the researchers used. Of course, it wasn’t all easy—some of the medical entries didn’t fit the right format, and not all the patients had genetic information available as well. But as clinicians hammer out some of the issues with electronic medical records and genetic testing becomes more common, this type of dataset will surely improve in the future.

In upcoming studies the researchers hope to continue to identify inherited genes that provide the underpinnings for contemporary diseases. If scientists can better understand the diseases themselves, they may also be able to develop more effective treatments.

Correction 2/12/2016, 1:00 p.m.: This article previously stated that 1.5 to 4 percent of the DNA in both Europeans and Asians is Neanderthal. That is the correct percentage for Europeans, but it’s actually higher in Asians. It’s been corrected and we apologize for the error.