It’s been 40,000 years since the Neanderthals disappeared, but their lingering genetic legacy may be influencing your health.

If you are of Asian or European descent, about 2 percent of your genome came from your Neanderthal ancestors, scientists say. Now, new evidence suggests this inheritance affects a broad range of health disorders including skin disease, your ability to fight infection and even your risk of addiction and depression.

Photo shows reconstructions of a Neanderthal man, left, and woman at the Neanderthal museum in Mettmann, Germany. A study in the journal Science says a person’s risk of becoming depressed or hooked on smoking may be influenced by Neanderthal DNA. The Associated Press

“Some of the associations we found made a lot of sense when we saw them, but the ones that affected neurological and psychiatric traits – those were surprising,” said Tony Capra, a computational geneticist at Vanderbilt University in Nashville who oversaw the research.

About 50,000 years ago, the anatomically modern humans who left Africa encountered Neanderthal settlements somewhere in the Middle East, scientists believe. The question of whether the two groups interbred was debated in scientific circles for decades, until 2010 when researchers found clear evidence of Neanderthal DNA sequences in people alive today.

Since then, genetic archaeologists have been trying to determine what instructions these Neanderthal genes contain code for and why they have been preserved over so many millenniums.

The new study, published Thursday in the journal Science, is based on data collected by the eMerge network, which includes the medical records and matching DNA sequences of 28,000 people in the United States. The researchers also worked with a previously published map of all the places where genetic variants derived from Neanderthals had been found in the human genome.

Armed with these two data sets, the team analyzed each of the 28,000 individuals in the consortium and determined whether they had the signatures of Neanderthal DNA in any of the known spots on the genome. Then, they looked for patterns that would indicate whether having these Neanderthal variants meant a person was more or less likely to have been diagnosed with a specific disease.

Most geneticists believe that at least some of the Neanderthal DNA variants that remain in the human genome were able to spread because they provided some advantage to our ancestors after they left Africa.

The strongest signal the researchers found involved a Neanderthal variant that improves the blood’s ability to clot, or coagulate. Today, too much clotting is considered a disorder because it increases risk of stroke, pulmonary embolisms and pregnancy complications, but tens of thousands of years ago, this hypercoagulation might have served our ancestors well.

The researchers also discovered an association between Neanderthal versions of genes and keratosis, which are skin lesions that can form after too much exposure to the sun. Neanderthal variants also were associated with an increased risk of mood disorders, tobacco addiction and a relatively strong effect on depression.

The researchers also found that Neanderthal DNA variants had a subtle but real association with disorders including obesity, respiratory infections, and the hardening of the arteries known as coronary atherosclerosis.

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