I think very, very, few people would be shocked to learn that one of Michelle Obama's ancestors were white. But I could be wrong:

Viewed by many as a powerful symbol of black advancement, Mrs. Obama grew up with only a vague sense of her ancestry, aides and relatives said. During the presidential campaign, the family learned about one paternal great-great-grandfather, a former slave from South Carolina, but the rest of Mrs. Obama's roots were a mystery.

Now the more complete map of Mrs. Obama's ancestors -- including the slave mother, white father and their biracial son, Dolphus T. Shields -- for the first time fully connects the first African-American first lady to the history of slavery, tracing their five-generation journey from bondage to a front-row seat to the presidency.

I'm not sure why this is news. Still, there is one advantage here. People who think Barack Obama "isn't really black," are now free to extend that logic to Michelle. One day they'll realize that, by their lights, no one is. Or not.