"It's tempting to think that Neanderthals were already adapted to the non-African environment and provided this genetic benefit to (modern) humans," said Prof David Reich, from Harvard Medical School, co-author of the paper in Nature.
But other gene variants influenced human illnesses, such as type 2 diabetes,
long-term depression, lupus, billiary cirrhosis - an autoimmune disease of the
liver - and Crohn's disease. In the case of Crohn's, Neanderthals passed on
different markers that increase and decrease the risk of disease.
Asked whether our ancient relatives actually suffered from these diseases
too, or whether the mutations in question only affected the risk of illness when
transplanted to a modern human genetic background, Mr Sankararaman said: "We
don't have the fine knowledge of the genetics of Neanderthals to answer this,"
but added that further study of their genomes might shed light on this
Joshua Akey, from the University of Washington, an author of the Science
publication, added: "Admixture happened relatively recently in evolutionary
terms, so you wouldn't expect all the Neanderthal DNA to have been washed away
by this point.
"I think what we're seeing to a large extent is the dying remains of this
extinct genome as it is slowly purged from the human population."