Foster et al. reply

It had been suggested to us earlier (by Herbert Barger, who also helped to recruit the descendants of Field Jefferson who participated in our study) that Isham Jefferson, son of Thomas Jefferson's brother Randolph, might have been the father of one or more of Sally Hemings’ children. Barger's proposal was based on a statement5 that Isham was reared by Thomas Jefferson; he suggested that Isham could have been at Monticello or at Snowden (Snowden was across the James River from Scottsville, which is about 20 miles from Monticello) when Eston Hemings was conceived. But it is not known for certain that Isham was at Monticello at that time, whereas it is documented that Thomas Jefferson was. From the historical knowledge we have, we cannot conclude that Isham, or any other member of the Jefferson family, was as likely as Thomas Jefferson to have fathered Eston Hemings.

We know from the historical and the DNA data that Thomas Jefferson can neither be definitely excluded nor solely implicated in the paternity of illegitimate children with his slave Sally Hemings. When we embarked on this study, we knew that the results could not be conclusive, but we hoped to obtain some objective data that would tilt the weight of evidence in one direction or another. We think we have provided such data and that the modest, probabilistic interpretations we have made are tenable at present.

See also David M. Abbey and Gary Davis