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http://gunnyg.wordpress.com/2009/05/26/the-five-black-presidents-of-the-united-states-of-america/
Interesting article. The conclusions are certainly plausible. There was considerable inter-racial cross-breeding and sometimes marriage in the early colonies, so much so that Virginia found it necessary to define “mulatto” for at least some purposes. Mixed-race individuals defined as “mulatto” by a 1705 Virginia statute were “the child of an Indian, or the child, grandchild, or great grandchild of a Negro.” Ch. IV, 3 Laws of Va. 252 (Henning 1823)— meaning that a 1-16th African (otherwise European) could be considered “white.” The Melungeons of southern Appalachia have been shown to be primarily a mix of northern European and sub-Saharan African ancestors.