Genes can’t tell us if US president James Madison fathered a child with a slave.

Several years ago newspapers reported that a study of DNA proved that Thomas Jefferson, the author of the Declaration of Independence, had fathered children with his slave Sally Hemings. Now some African-Americans want a genetic history to prove that they are descended from James Madison, the father of the US constitution. But DNA can’t prove what they want.

The Washington Post reports that Bettye Kearse, an African-American physician, wants to confirm her family’s oral tradition that they are direct descendants of Madison. This past weekend she attended the Montpelier slave descendants reunion at the fourth president’s mansion. "Working with Bruce Jackson, co-director of the Roots Project, which helps African Americans trace their genetic histories," Kearse wants to:

compare the Y chromosomes – which are identical across generations – of male descendants in Madison’s family to the Y chromosomes of some of Kearse’s male cousins. Jackson and Kearse have been searching for Madison relatives in England but recently located a descendant of one of Madison’s brothers in North Carolina.

begins with a kidnapped African slave, Mandy, who Kearse says was impregnated at Montpelier by Madison’s father. The child, Coreen, later gave birth to Madison’s child, whom she named James Madison.

Jackson, speaking to attendees Saturday about how genetic research is conducted, noted that if Kearse’s claim proves correct, it would mean Madison’s only living direct descendants are African American.

A more accurate headline, of course, would have been "A Jefferson – not necessarily Thomas Jefferson – fathered" Sally Hemings’ youngest child.) The article on the DNA test results was accompanied by an article "Founding father," co-authored by Professor [Joseph] Ellis, which proclaimed that the DNA analysis "confirms that Jefferson was indeed the father of at least one of Hemings’ children."

Jefferson’s place in American history – his central role in our nation’s founding and the evolution of its system of government – justly derives from his ideas. As I see it, genealogy is irrelevant: the true "children" of Jefferson today are those who understand his ideas and work to keep them alive. His lasting legacy is the body of ideas he has given us, ideas still quite relevant today, to the perennial problems of protecting individual rights and limiting the powers of government.