“This level is what you would expect in someone who had a great-grandparent who was African,” said Kari Stefansson of deCODE Genetics, the company responsible for the analysis.

“It was very surprising to get this result for Jim."

Watson recently resigned as chancellor of the Cold Springs Harbor laboratory after controversial remarks he made provoked a furore around the world.

In an interview, Watson claimed to be 'inherently gloomy about the prospects for Africa' as 'all our social policies are based on the fact that their intelligence is the same as ours - whereas all the testing says not really.'

But deCODE's analysis of Dr Watson's genome shows 16 of his genes probably came from a black ancestor of African origin.

By contrast, most people of European origin would have no more than one gene of this type.

A further nine of Watson's genes may have come from an ancestor of Asian descent.

Watson consented to the results of the analysis to be published on the internet in the interests of science and research.

Critics of Watson's remarks on race and intelligence are no doubt appreciating the deep irony of these revelations.

"I never did agree with Watson's remarks," said John Sulston, fellow Nobel laureate and one of the leading contributors to the Human Genome Project.

"We don't understand enough about intelligence to generalise about race."