Debate over whether to call this son of a White Kansan and a Black Kenyan biracial, African-American, mixed-race, half-and-half, multiracial — or, in Obama's own words, a “mutt” — has reached a crescendo since Obama's election shattered assumptions about race.

Obama has said, “I identify as African-American — that’s how I’m treated and that’s how I’m viewed. I’m proud of it.” In other words, the world gave Obama no choice but to be Black, and he was happy to oblige.

But the world has changed since the young Obama found his place in it.

Intermarriage and the decline of racism are dissolving ancient definitions. The candidate Obama, in achieving what many thought impossible, was treated differently from previous Black generations. And many White and mixed-race people now view President-elect Obama as something other than Black.

So what now for racial categories born of a time when those from far-off lands were property rather than people, or enemy instead of family?

"They're falling apart," said Dr. Marty Favor, a Dartmouth professor of African and African-American studies and author of the book Authentic Blackness.

"In 1903, W.E.B. DuBois said the question of the 20th century is the question of the color line, which is a simplistic Black-White thing," said Favor, who is biracial. "This is the moment in the 21st century when we're stepping across that."

Rebecca Walker, a 38-year-old writer with light brown skin who is of Russian, African, Irish, Scottish and Native American descent, said she used to identify herself as "human," which upset people of all backgrounds. So she went back to multiracial or biracial, "but only because there has yet to be a way of breaking through the need to racially identify and be identified by the culture at large."