Neanderthal DNA linked to diseases
If you are a hairy diabetic who smokes and suffers from stomach cramps, blame your Neanderthal ancestry.
Remnants of Neanderthal DNA in the genes of non-African modern humans are linked to a range of health problems, including Type 2 diabetes, Crohn's disease, lupus and biliary cirrhosis, a study has shown.
They are also associated with smoking behaviour and thick hair, as well as tough skin and nails.
Between 2% and 4% of the genome, or genetic code map, of Europeans and Asians is believed to be a legacy of interbreeding between ancient Homo sapiens and Neanderthals.
The two were separate human subspecies who co-existed on Earth for thousands of years until the Neanderthals became extinct around 30,000 years ago.
Indigenous people from sub-Saharan Africa, whose ancestors did not migrate out of the continent to breed with Eurasian Neanderthals, carry little or no Neanderthal DNA.
A new DNA comparison study has now shone a spotlight on important aspects of Neanderthal inheritance.
Scientists compared genetic variants in the DNA of 846 people of non-African heritage, 176 people from sub-Saharan Africa, and the toe bone of a 50,000-year-old Neanderthal woman.
A near-complete reconstruction of the Neanderthal's genome was published last year.
The team identified some areas of the modern non-African genetic code that were rich in Neanderthal DNA while others looked like Neanderthal-free zones.
A number of variants inherited from Neanderthals were linked to diseases, especially autoimmune disorders.
Crohn's, which causes inflammation of the gut, lupus and the liver disease biliary cirrhosis are all problems triggered by an over-zealous immune system.
In addition, one genetic variant, or "allele", was associated with smoking behaviour, specifically in Europeans.
Professor David Reich, from Harvard Medical School in the US, who led the study reported in the journal Nature, said: "Now that we can estimate the probability that a particular genetic variant arose from Neanderthals, we can begin to understand how that inherited DNA affects us.
"We may also learn more about what Neanderthals themselves were like."
Among the discoveries was the fact that Neanderthal ancestry could be seen in genes for keratin filaments, a fibrous protein that lends toughness to skin, hair and nails.
This may have helped provide the newcomers from Africa thicker insulation against the cold European climate.
"It's tempting to think that Neanderthals were already adapted to the non-African environment and provided this genetic benefit to (modern) humans," Prof Reich said.
The "desert" regions that contained far less Neanderthal DNA than average were associated with male fertility.
This suggests that the two sub-species were sufficiently far apart to put them "at the edge of biological incompatibility", according to the professor.
Ancient modern human and Neanderthal populations apparently found it hard to breed successfully after 500,000 years of evolutionary separation.
The team is following up the research by testing for Neanderthal mutations in a biobank containing genetic data from half a million Britons.
Professor Chris Stringer, a leading expert in human origins at London's Natural History Museum, said the findings added a new twist to the debate over how early modern humans related to Neanderthals and Denisovans, another subspecies cousin from Siberia.
He did not think it undermined current thinking about our ancestors' African origins.
"The genetic data also show there are thousands of DNA changes that are unique to Homo sapiens, and these distinctions are likely to have accumulated during the several hundred thousand years since Homo sapiens separated from the Neanderthal and Denisovan lineages as they evolved in Africa and Eurasia, respectively," he said.
"Our genetic heritage is still largely from a recent African origin, despite the interbreeding with other human populations that undoubtedly occurred."
A parallel study in the journal Science suggests that up to a fifth of the Neanderthal genome may have survived in modern human populations.
This was despite the fact that the proportion of Neanderthal DNA in any one individual is low, around 2% to 4%.
The US scientists, from the University of Washington, Seattle, compared ancient and modern DNA sequences in 600 present-day humans from Europe and East Asia.