Henry Louis Gates, Jr., writing in The Root after the discovery of Michele Obama's white ancestor:
the social categories of “white” and “black” are and always have been more porous than can be imagined, especially in that nether world called slavery.
As I have learned since embarking upon my African American Lives series (for PBS), never before are more African Americans determined to ferret out the names of their slave ancestors, and never before have more resources, especially online, been available to facilitate these searches. But, be prepared. To paraphrase the Bible: seek; but fasten your seat belt as to what ye may find.
Specifically, only 5 percent of African-Americans can claim at least one Native American great-grandparent; but 58 percent can claim at least one white great-grandparent (or the equivalent thereof). The past is what it is, not what we may wish it was.