Did the revered founding father of America, Thomas Jefferson, have an illegitimate child by a slave, Sally Hemings?
Often dismissed by historians as a smear on the man whose head is on both Mount Rushmore and the national currency, the paternity claim is now upheld by scientists armed with DNA findings.
The fact that the author of the Declaration of Independence proclaiming "all men are created equal", kept slaves has long been an embarrassing puzzle for Americans. Now they will have to come to terms with Jefferson's fathering at least one slave child.
Jefferson strongly disapproved of the mixing of races, writing that "the amalgamation of whites with blacks produces a degradation to which no lover of his country, no lover of excellence in the human character can innocently consent".
The results of blood tests on descendants of Jefferson, the country's third president, and Hemings show he is almost certainly the father of her youngest son, Eston Hemings. The results of the tests are reported in the latest issue of the scientific journal, Nature.
The Hemings family has long believed that they are descended from Jefferson, who freed their ancestors from slavery at his death. Dr Eugene Foster, a retired university pathologist in Virginia, decided to test the claim through the Y chromosome in the genetic make-up, which passes virtually unchanged from father to son.
Geneticists at Oxford and Leiden Universities analysed the blood samples taken from Jefferson and Hemings descendants. Dr Eric Lander, a DNA expert at the Whitehead Institute in Boston, writes in Nature: "There is such a strong case that Jefferson had a liaison with Hemings that the DNA evidence converts that possibility into a near certainty."
One of the blood samples was taken from Mr John Jefferson (52) of Norrisville, Pennsylvania. When told of the findings by the New York Times, Mr Jefferson said he was not really surprised that he was descended from a president and his slave. "I've known it all my life," he said.
A surprise result of the tests was that Jefferson was not the father of Sally Hemings's eldest son, Tom, who was born soon after her return in 1789 from Paris, where she had been a maid to Jefferson (then the US ambassador to France).
Striking a contemporary note, Dr Lander writes: "Now with impeccable timing, Jefferson reappears to remind us of a truth that should be self-evident. Our heroes, - and especially presidents - are not gods or saints, but flesh-and-blood humans."