II. Assessment of DNA Study

Report of the Research Committee
on Thomas Jefferson and Sally Hemings

Thomas Jefferson Foundation
January 2000

II. Assessment of DNA Study

The committee believes the design and methodology of the DNA analysis reported by Dr. Eugene Foster et al. in the journal Nature is sound and straightforward and meets the current standards of the scientific community. The laboratories involved are highly reputable in Y-chromosomal studies and have extensive records of publication in scientific peer-reviewed journals. The study compared nineteen genetic markers on the Y chromosomes of fourteen subjects-five male-line descendants of two sons of Field Jefferson (Thomas Jefferson's paternal uncle), three male-line descendants of three sons of John Carr (grandfather of Samuel and Peter Carr), five male-line descendants of two sons of Thomas Woodson, and one male-line descendant of Eston Hemings.

The results clearly show that the male-line descendants of Field Jefferson and Eston Hemings have identical Y-chromosome haplotypes (the particular combination of variants at defined loci on the chromosome). Scientists note that there is less than a 1 percent probability that this is due to chance. Thus the haplotype match is over one hundred times more likely when Jefferson and Eston Hemings are genetically related through the male line. This study by itself does not establish that Hemings's father was Thomas Jefferson, only that Hemings's father was a Jefferson.

Because of the absence of a match between the Carr and Hemings haplotypes, the study rules out both Samuel and Peter Carr as Eston Hemings's father. Since the Jefferson and Woodson haplotypes also did not match, the study indicates that Thomas Woodson's father was not a Jefferson. We note that the design of the study eliminates any ambiguity resulting from the genetic influence of John Wayles, Thomas Jefferson's father-in-law and Sally Hemings's alleged father, by looking at markers only on the Y chromosome. DNA of male-line descendants of five "old Virginia families" was also included in the analysis in an attempt to sample the local population of Y chromosomes. None matched the Jefferson haplotype, one that is considered quite rare.

The committee is aware that further DNA testing, coordinated by Dr. Foster, is in progress.

For comments of scientists consulted, see Appendix B.

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