Science1 publisher2 min readPublished
Preprint puts Jefferson at 99.96 percent likely to have fathered a son with Sally Hemings
A bioRxiv preprint puts Thomas Jefferson near 99.96 percent likely to have fathered at least one of Sally Hemings's sons, using DNA from locks of his preserved hair. A 1998 Y-chromosome test could point only to the Jefferson male line, and the analysis behind the new figure has not been peer-reviewed.
The Scientist · Science desk
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What happened
- One of the sequenced hair locks came from a Monticello packet annotated as cut by Jefferson's grandson-in-law, Nicholas P. Trist, just after Jefferson died on July 4, 1826.
- The team compared the hair DNA with saliva from 16 living members of the Jefferson and Hemings families, among them descendants of Sally Hemings's sons Eston and Madison.
- For those two sons the comparison weighed three possible fathers: Thomas Jefferson, his brother Randolph, or one of Randolph's own sons.
- The Thomas Jefferson Foundation says he is thought to have fathered at least six of Hemings's children after his wife, Martha, died in 1782, four of them surviving to adulthood.
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Why it matters
- capability Reading the whole genome, not just the shared Y chromosome, can tell apart close male relatives who otherwise look identical on the paternal line.
- constraint That figure covers at least one of two sons, Eston and Madison. Descendants of Hemings's other recorded children, Beverly and Harriet, have not been located to test.
- contradiction Some of Jefferson's relatives had blamed his nephews Peter and Samuel Carr; the comparison instead favours Thomas over both his brother Randolph and Randolph's sons.
The 1998 test that reopened the case read only the Y chromosome, which a father passes to his sons almost unchanged. It matched a male-line descendant of Eston Hemings to the Jefferson paternal line, according to the Thomas Jefferson Heritage Society [7]. Every Jefferson man carries that chromosome, and about 25 adult male Jeffersons were living in Virginia at the time, several of them visitors to Monticello [8]. The match applied to the whole line. The researchers judged Thomas Jefferson the most plausible father, but the test could not settle it [8].
The new preprint works from the rest of the genome [3]. The hair samples all lacked follicles, but the researchers extracted, sequenced and analysed DNA from them anyway [9]. The three men in the comparison belong to the same Jefferson paternal line, so a Y-chromosome test cannot separate them; instead the authors searched for genomic segments that living Hemings and Jefferson descendants inherited from a common ancestor [3][12]. On that reading, Thomas Jefferson fits best, at about 99.96 percent for fathering at least one of Eston and Madison, ahead of the scenarios that name his brother or a nephew [3][12].
Historians had suspected the relationship for two centuries, and it drew heavy attention during Jefferson's first term and became one of the largest presidential scandals in American history [1][14]. Still, the principals left little on the record: Jefferson made no public or private comment, and Hemings left no known account of her own [5].
What to watch
- Whether the preprint clears peer review and where it is finally published.
- Whether researchers can locate living descendants of Beverly and Harriet to extend the test.
- How the Monticello foundation and the Jefferson Heritage Society respond to the whole-genome result.