Growing up in Philadelphia, Mat Johnson lived mostly with his mother in a black neighborhood. The son of an African-American mother and an Irish-American father, his skin was so light that he might have passed for white. But being biracial meant only one thing back in the '70s: "Um, it meant: black," Johnson says with a laugh. "There wasn't a lot of ambiguity there. I didn't hear the world biracial or didn't think of myself as biracial. And when I did hear that, I reacted to it defensively.