So what if Elizabeth Warren claims to be part Native American? She’s entitled, according to historical documents. Besides, Americans never have been all that clear or consistent about what distinguishes one race from another.

Republican Sen. Scott Brown, of Massachusetts, is calling on his Democratic challenger Warren to clear the air over questions raised by the Boston Herald as to whether she used her ancient and diluted Indian heritage to give herself an unfair employment advantage.

At least she’s not lying about her background. Historical records appear to confirm that she has Cherokee ancestors. But is her background Indian enough?

That question looms after researcher Christopher Child at the New England Historic Genealogical Society turned up evidence of her Indian blood. A transcript of an 1894 marriage application shows Warren’s great-great-great-grandmother listed herself as Cherokee.

That would make Warren 1/32nd Native American, although it is possible that more recent Indian ancestors could be turned up in further research. Child also found that Warren’s great-grandfather, John Houston Crawford, lived in Native American territory but identified himself as white in the 1900 census.

However, Warren’s family is not included in the official Dawes Commission rolls, a census of major tribes completed in the early 20th century that Cherokees use to determine tribal citizenship.

Such a tenuous tie to her Indian past has led critics at the Boston Herald, which broke the story, to label her “Fauxcahontas,” among other nicknames. Yet, I would ask, how much Indian blood do you need these days to claim Indian heritage?

In other words, whatever happened to the one-drop rule?

That’s the rule in America’s past, you may recall, that declared anyone who had at least “one drop” of “black blood” to be black. The irony of this rule, invented by slave masters who wanted to have more slaves, is how it has been encouraged in modern times, particularly by black leaders who want to have more blacks in our ranks.

But like other rules of race, this one is not applied uniformly or consistently. George Zimmerman, the man accused of killing Trayvon Martin in Florida, had an Afro-Peruvian great-grandfather on his mother’s side, according to his family. That would make him at least one-eighth black, which is a lot more than Warren is Indian. Yet Zimmerman was reported first as “white,” then a “white Hispanic.” If the old one-drop rule applies, he also could be called a white-Hispanic black.

If taken literally, that would make the killing of Martin, about whose blackness there is no confusion, a black-on-black crime -- which, sad to say, attracts a lot less national attention than similar violence that crosses racial lines.

Zimmerman is not likely to be seen as black by many people. But, like the Warren controversy, he illustrates how quickly our old racial narratives are failing to keep up with changing times.

The Herald reported that Warren used to list herself as Native American in law school directories while teaching at several law schools across the country in the 1980s and ‘90s.

She dropped the reference from her biography after she was hired at Harvard Law School in the 1990s at a time when protesting students and faculty had been pressuring the school to hire more minority female faculty. The law school says it has one faculty member of Native American heritage, according to reports, but won’t say which one.

If Warren was claiming Indian ancestry when it worked to her benefit, she was following another American tradition, writes David Treur, an Ojibwe Indian from northern Minnesota and author of “Rez Life: An Indian’s Journey Through Reservation Life.”

“An Indian identity has become a commodity,” he recently wrote in The Washington Post, “though not one that is openly traded. It has real value in only a few places; the academy is one of them. And like most commodities, it is largely controlled by the elite.”

Race is no longer as simple as black and white, but then it never really was. The real issue of what Warren, Zimmerman and the rest of us want to call ourselves has two sides: how we see ourselves and how we are seen by others.

If anything, Treur is right about elites. The Warren controversy illustrates how rapidly the one-drop rule and other old rules of race are fading at a time when race is becoming less of a problem than privilege -- who has it and who doesn’t -- regardless of race.