Elizabeth Warren, the U.S. Senate candidate who claimed minority status during law school and as a young law professor, continues to insist that she is 1/32 Native American. Warren’s only proof is her mother’s word. Many American families have stories about Native American ancestors. How many really do?

At least a few percent of the population. While just 1.7 percent of Americans self-identified as either completely or partially Native American on the 2010 census, the Cornell University Genetic Ancestry Project used genetic tests to identify Native American heritage in between 4 percent and 5 percent of the 200 undergraduates studied. That sample isn’t necessarily representative of the general population, because the students who volunteered themselves were likely curious about their backgrounds, but other projects of approximately the same size have produced similar findings. There doesn’t seem to be much correlation between an individual’s expectation and their actual ancestry, however. Many of the Cornell students who were found to have Native American blood expected to be exclusively European, and geneticists say the overwhelming majority of white Americans who expect to find Native American ancestry in their DNA are disappointed. …

The weakness of the genetic tests poses an even bigger problem when you’re looking for Native American ancestors. Native Americans have been reluctant to participate in genetic testing, which means scientists don’t have many reliable markers for that population. In addition, the genetic profiles that have been conducted show that many card-carrying members of certain tribes, such as the Cherokee, have more European ancestors than Native American ancestors. That means even the small number of Native American genetic markers we know of aren’t present in large segments of the population, making it difficult to find evidence of Native American DNA in people like Elizabeth Warren. That’s part of the reason that most Native American tribes have resisted using ancestral genetic analyses to determine membership. Tribal membership has more to do with the culture and location of one’s ancestors than precisely how many of their relatives can be traced back to the Bering land bridge.