He was 81.
Foster died Monday at the University of Virginia Medical Center in Charlottesville after a battle with prostate cancer and leukemia, the New York Times reported.
Nearly two centuries of gossip speculated that a relationship between Jefferson, the third president of the United States, and Hemings had resulted in the birth of at least one child. Foster and historian Winifred Bennett embarked on a mission in 1996 to use DNA testing to trace a possible link, the newspaper said.
Foster used a new genetic technique of tracing ancestry through the Y chromosome, which descends through the male line. He found that the Y chromosome of a descendant of Hemings' son, Eston, matched that of Jefferson's lineage.
The findings were published in 1998 in the journal Nature.