As it happens, Samuel Bunch was my great great great great great grandfather (and Barack Obama is my 5th cousin twice removed - our most recent common male ancestor was Samuel's son Charles). I had no knowledge of any mixed race ancestry prior to about a year ago. At that time, I submitted some cheek scrapings to Family Tree DNA. My y-haplogroup turned out to be E1b1a, which is pretty much diagnostic for a recent origination from sub-Saharan Africa.