Oxford University scientists have used DNA to produce compelling evidence that American president Thomas Jefferson fathered a love child by his slave.

Jefferson, one of America's founding fathers, has been at the centre of a mystery for 200 years over the nature of his relationship with Sally Hemings.

She was his slave and believed to have been his mistress.

Now Dr Chris Tyler-Smith and Ms Tatiana Zerjal, of Oxford University's department of biochemistry, have discovered evidence that the US president and author of the Declaration of Independence fathered a child with one of his slaves, but it was not the child some historians have previously thought.

It was widely believed that Thomas Woodson, Sally Hemings's first son, had been fathered by Jefferson.

However, the Oxford scientists, who worked alongside other academicsrof Peter Donnelly, of Leicester University and Leiden University in the Netherlands, and Prof Eugene Foster, a retired pathologist from Virginia, have discovered strong evidence that Jefferson fathered another of Sally Hemings's children - her youngest son, Eston Hemings Jefferson.

The scientists studied blood samples from descendants of both Jefferson, Hemings and from Jefferson's nephews to address the theory that one of them had fathered Hemings's children.

During the 18-month study, samples were coded with numbers and divided among three laboratories in Oxford, Leicester and Leiden, Holland.

Dr Tyler-Smith, a University research lecturer, told the Oxford Mail that although the research proved a Jefferson fathered Eston, it did not prove which one.

He said: "We rely on history to tell us which Jefferson it is."

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