Mr. Turner, a professor at the University of Virginia, is editor of The Jefferson-Hemings Controversy: Report of the Scholars Commission (Carolina Academic Press, 2011).

Thomas Jefferson has long been celebrated in America as the principal author of the Declaration of Independence. But his iconic status has diminished in recent years thanks to a widespread belief that he fathered a child by Sally Hemings, his enslaved servant.

In reality, the 1998 DNA tests alleged to prove this did not involve genetic material from Thomas Jefferson. All they established was that one of more than two dozen Jefferson males probably fathered Sally Hemings's youngest son, Eston. And there is good reason to believe that at least seven Jefferson men (including the president) were at Monticello when Eston was conceived in the summer of 1807.

Allegations that the "oral history" of Sally's descendants identified the president as the father of all of Sally's children are also incorrect. Eston's descendants repeatedly acknowledged—before and after the DNA tests—that as children they were told they were not descendants of Thomas Jefferson but rather of an "uncle."

A more plausible candidate is Thomas Jefferson's younger brother, known at Monticello as "Uncle Randolph."...