A scientific study claims to have resolved a long-standing historical debate about whether Thomas Jefferson, the third president of the United States, had a relationship with Sally Hemings, an enslaved woman who lived in his household. The research was detailed in a book titled History by a hair, published by Penguin Random House and led by Richard Kurin, a senior researcher at the Smithsonian Institution. The study involved a 15-year collaboration among archaeologists, genealogists, molecular geneticists, and historians, aiming to determine if the descendants of the Hemings family share the same DNA as Jefferson. The research team used advanced DNA analysis techniques to overcome past challenges, including the lack of usable DNA from Jefferson himself. They examined preserved hair samples from Jefferson and compared the genetic markers with those of living descendants of the Hemings family. The study identified mitochondrial DNA, which is inherited from the mother, and the Y chromosome, which is inherited from the father, both of which matched the expected genetic lineage of Jefferson and the Hemings family. The researchers also sequenced Jefferson's genome, allowing them to compare the shared DNA percentages between Jefferson and his descendants. The study found that the genetic similarity between Jefferson and the descendants of Eston Hemings, a son of Sally Hemings, was consistent with a direct paternal relationship. After running 20,000 simulations of different paternity scenarios, the probability that Jefferson is not the father of Eston Hemings was found to be less than one in a thousand. The study used advanced bio-informatics tools to process millions of small DNA fragments and compare them to a reference genome, enabling the analysis of genetic information from a very small amount of material. This method is also used in criminal investigations to solve cold cases. The research was conducted despite challenges such as leadership changes at the Smithsonian and tensions with the Trump administration. The findings were anticipated but have not yet been published in a peer-reviewed journal.