Researchers have found correlations between Neandertal-derived genes and disease states in modern humans – including those influencing the skin, the immune system, depression, addiction, and metabolism. The results show how ancient liaisons between Neandertals and anatomically modern humans (AMH) continue to impact our genetic heritage. Previous studies have suggested that when AMH populations migrated out of Africa, they interbred with Neandertals. More recently, scientists have identified parts of the human genome carrying Neandertal genetic variants, but – in part because Neandertal-derived DNA is so hard to identify and also because of the expense of performing tests for its influence on individuals – scientists still don't fully understand how Neandertal-derived variants influence modern human traits. Now, by comparing a recent genome-wide map of Neanderthal haplotypes, or gene groups, with health records of 28,000 adults of European ancestry, Corinne Simoniti and colleagues have documented the lingering effects of Neandertal-derived alleles. The researchers first defined about 135,000 "high-confidence" Neandertal genetic variations (or SNPs) in modern humans. Next, they looked at the relationships between these SNPs and conditions Neandertal-derived alleles are thought to influence, ultimately finding that Neandertal alleles were significantly correlated with the risk for 12 traits, including depression, myocardial infarction, and blood disorders. It is possible, the authors say, that some Neandertal alleles provided a benefit in early AMH populations as they moved out of Africa, but then became detrimental in modern Western environments.