In 1998, DNA testing showed that someone from Jefferson's male line must have been the father of Hemings's son Eston. Scientists tested the Y chromosome of Jefferson's uncle and the Y chromosome of Jefferson's nephews' grandfather on their own father's side. They compared these chromosomes to the Y chromosomes of Eston's male descendants. They found that Eston's family had Y chromosomes like Jefferson's and not like his nephews'. Before the tests, about a third of historians believed Thomas Jefferson had been the father of Hemings' children, about a third did not, and about a third were undecided. After the test, about two thirds believed Thomas Jefferson was the father of Hemings' children.