For over 200 years, Americans have debated whether Thomas Jefferson fathered children with Sally Hemings, the enslaved woman at his Monticello estate. The Smithsonian Institution now says it has the most definitive evidence yet, based on Thomas Jefferson’s genome sequenced from strands of his hair. In a new book, Richard Kurin, the Smithsonian scholar who led the effort, describes how researchers used advanced techniques to extract and compare Jefferson’s DNA with samples from 13 living Hemings and Jefferson family descendants. Kurin calls the findings “extraordinary proof” that Jefferson fathered Hemings’s children, though he acknowledges other perspectives remain.

The book, “History By a Hair,” is set for release on Sept. 22 by Crown, a division of Penguin Random House. However, its rollout has been affected by the ongoing standoff between the Smithsonian and the Trump administration, which has accused the institution of promoting “divisive, race-centered ideology.” Smithsonian Secretary Lonnie G. Bunch III, who has led the organization since 2019, recently announced his planned departure by year-end.

Originally dismissed, the claim of a relationship between Jefferson and Hemings dates to the early Republic, when political opponents accused him of keeping an enslaved Black mistress. Generations of Hemings family accounts, including an 1873 oral history from her son Madison, supported the claim. The new DNA evidence adds scientific weight to that legacy.