Beverly Hemmings? Who the hell is that?
According to whom? Even circumstantial evidence has to be EVIDENCE, dear.
Oral history? You mean the Hemings family passing down rumors that they were really descended from Thomas Jefferson? Well, gee. Who wouldn't like to believe they were descended from a former President and Founding Father, rather than, for example, his halfwit younger brother? My family likes to talk about being descended from Jefferson Davis. The difference is, we also have hard evidence like birth records to back it up, not just "oral history".
I not only have no clue who Mary Chestnut is, I also have no idea why her vague personal opinion on something general has anything to do with this.