Although there had long been speculation in the family and by historians, geneticists at Leicester and Oxford universities and Leiden university in the Netherlands were able to confirm it to a reasonable degree of certainty.
They compared genetic material from the descendants of Ms Hemings and of Jefferson's paternal uncle. They found a match between DNA from the family of Eston Hemings, one of Ms Hemings' sons. There was no match with the descendants of Thomas Woodson, who had long been believed to be Jefferson's offspring. The case is reported in the current edition of Nature.
The report shows the extraordinarily complex sexual relationships that developed in the slave-owning areas of America.
Ms Hemings was herself the daughter of a slave and a slave-owner. She was, in fact, the half-sister of Jefferson's wife, Martha. After Martha died in 1782, Jefferson never remarried. Ms Hemings was sent in 1786 to Paris to accompany Jefferson's daughter, Mary, on the trip. She became his mistress there, and returned with him to Monticello, the family estate in Virginia, in 1789. She herself was fair-skinned, and each of her children was more so.
But Jefferson - the author of the Declaration of Independence, but a defender of the rights of slave-owners - never acknowledged the children. The discovery may mean that at last Ms Hemings and Jefferson's descendants can be buried at Monticello. So far, that right has been conferred only on his white family.
The affair became the subject of a scandal in 1802 when James Callender, an alcoholic Scottish journalist, blackmailed the then president Jefferson and broke the story in the press. Next July, ominously for the current president's detractors, Callender was found dead in the James river.
"Now, with impeccable timing, Jefferson reappears to remind us of a truth that should be self-evident," wrote geneticist Eric Lander and historian Joseph Ellis in Nature.
"Our heroes - and especially presidents - are not gods or saints, but flesh and blood humans, with all the frailties and imperfections that this entails."Reuse content