Neanderthal-derived DNA influences our risk of certain diseases, including addiction, blood clots, skin conditions and depression, a recent study has found.
Europeans and Asians possess DNA derived from Neanderthal populations, which interbred with modern humans around 50,000 years ago, but it is not known how these genetic variants influence modern human traits.
In order to understand how Neanderthal DNA affects health traits, researchers compared genetic variants previously identified as being derived from Neanderthals with the health records of 28,000 people of European ancestry, testing their association with over 1600 traits and diseases.
'We found that Neanderthal DNA indeed does influence many traits in modern humans, and it's a diverse array of traits – so traits involved in the immune system, traits involved in our skin, but also psychiatric traits and neurological traits,' said study author Dr Tony Capra, Assistant Professor of Biological Sciences at Vanderbilt University, Tennessee.
He added that finding an association with depression was 'really unexpected', and 'some Neanderthal DNA increases your risk and other bits of Neanderthal DNA decrease your risk'.
Corinne Simonti, the study's first author, told the Guardian: 'The brain is incredibly complex, so it is reasonable to expect that introducing changes from a different evolutionary path might have negative consequences.'
It was confirmed in 2010 that up to four percent of modern European and Asian DNA is inherited from Neanderthals. It is believed that Neanderthals migrated from Africa first, and had more time to evolve favourable adaptations to Ice Age Europe. Later, when anatomically modern human (AMH) populations migrated north, they interbred with Neanderthals.
The authors suggest that some of the Neanderthal DNA would have been advantageous in early AMH populations, such as the rapid blood-clotting condition hypercoagulability, which would have helped wound healing. However, in the modern world this condition is linked to an increased risk of strokes. Similarly the sunburn hazard condition actinic keratosis probably wasn't too serious in Ice Age Europe, but the genes are maladaptive now.
Back at Vanderbilt, Dr Capra is still investigating. 'We're now working towards understanding how, at the molecular level, these bits of Neanderthal DNA are influencing these associations with the diseases we've found. It may help us understand how to better avoid them.'