I trust that the Sage of Howth, as my colleague Deaglan de Breadun recently referred to him, is feeling vindicated this past week. I speak of Conor Cruise O'Brien, though not in the context of his resignation from the UK Unionist Party.

Rather, he must be feeling pleased that DNA evidence has at last shown that former US president Thomas Jefferson, author of the Declaration of Independence, was indeed involved in an "inappropriate relationship" with one of his slave girls, Sally Hemings, and that she was the mother of at least one of his children.

Two years ago, in The Long Affair: Thomas Jefferson and the French Revolution, 1785-1800, O'Brien contended that Hemings was Jefferson's long-term concubine and that they had four children together. This claim provoked outrage from the considerable number of academics and others who still regard Jefferson as a great liberal hero, despite acknowledging his ownership of slaves and occasional savage treatment of them.

Now a team of geneticists has confirmed "to a reasonable degree of certainty" that Hemings had at least one child with Jefferson.

Some satisfaction, then, up at Howth Head. It's good to be proved correct, but even better when some people have been so loud and forceful in their denunciations. O'Brien's book was well received in some quarters. In this paper, Frank Callanan called it "a quietly devastating foray into the scripture of the American revolution", but elsewhere it did not go down so well.

In the Times Literary Supplement, Harvard professor of history Bernard Bailyn took a very dim view, particularly of the allegations about Sally Hemings: "Alone, I think, among current historians, he [O'Brien] is convinced that the slave girl was Jefferson's concubine and that together they had four children".

Well, not so alone any longer, presumably. Prof Bailyn went on to criticise the "tirade" of the book, its "empurpled indignation" and its "impassioned ideological warfare".

All good clean fun. The dreary side of this kind of thing is the predictable development. Just a few days after the recent Jefferson revelations, a woman from Illinois announced that she hopes to prove she is descended from George Washington.

Ms Janet Allen (44) says her ancestor West Ford was the mulatto son of the first American president and a plantation slave named Venus. According to Ms Allen, her great-great-great-grandfather West Ford was the result of a liaison begun in 1784 and lasting for a year or more. "We're trying to prove who we are", she told a Chicago newspaper: "This is where the battle lines are drawn". Fighting talk. But it is going to prove rather embarrassing if the founding father of America also turns out to be the father of a slave's unacknowledged son. Washington has always been revered by Americans for his adherence to the highest moral standards (partly derived, it seems, from his close study of a 16th century Jesuit compilation, and Roman notions of noble conduct).

And one of the most recent biographies of Washington, Richard Brookhiser's Founding Father - Rediscovering George Washington, contends, according to one reviewer, "that his exemplary life can and should provide a model of public leadership for the late 20th century United States".

You could say it already has, if Ms Allen's allegations are true.

Scholars have long argued that America's founding father was sterile, therefore incapable of fathering West Ford. At any rate, the Mount Vernon Ladies' Association, which manages George Washington's estate, has denied Ms Allen access to locks of Washington's hair, which might allow her to prove her claim by means of DNA testing.

Coincidentally, as it happens, I myself have good reason to believe I am a direct descendant of Benjamin Franklin, or if not him, possibly Abraham Lincoln.

So far, unfortunately, my team of geneticists, heraldic experts, genealogists, seers, astrologers, historians, fingerprint specialists, DNA scientists, solicitors and archivists has not turned up a great deal of evidence to lend substance to my claims, apart from a very interesting shred of cigar wrapper currently being examined in the Smithsonian Institution.

On the plus side, they have found irrefutable evidence that I could not possibly be a descendant of Calvin Coolidge.