Tribes establish their own criteria for membership. It does not involve 'looks' or genetics.
So what do they base it on?
And if tribes were purely private clubs, nobody would have an issue with them having arcane rules for membership. But belonging to a tribe can give you tax exemptions and a cut of tribal monopoly (and tax-free) businesses along with other benefits, like ability to not follow federal laws. I think all special treatment of Indians needs to end.
As mentioned before, Native Americans have not contributed enough samples to data bases such as Ancestry and 23andMe, etc. in order to establish any genetic markers particular to Native Americans or any particular tribe.
So in other words, Warren could have zero Indian ancestors instead of one as far back as ten generations ago.
Individuals enrolled in federally recognized tribes also receive a Certificate of Degree of Indian Blood (referred to as a CDIB) from the Bureau of Indian Affairs, specifying a certain degree of Indian blood, i.e., a blood quantum.
Isn't "blood quantum" just a crude proxy for genetics?
The Bureau of Indian Affairs uses a blood quantum definition—generally one-fourth Native American blood—and/or tribal membership to recognize an individual as Native American.
So Warren is out with her 1/1024.
However, each tribe has its own set of requirements—generally including a blood quantum—for membership (enrollment) of individuals. Typically, blood quantum is established by tracing ancestry back through time to a relative or relatives on earlier tribal rolls or censuses that recorded the relative's proportion of Native American blood. In such historical instances, the proportion was more often than not simply self-indicated.
Self-indicated? Like Warren did on her bar registration form? That opens the door to abuse. And genealogical data does not capture false paternity. Say Little Fawn is married to Flying Eagle but has an affair with Peter Johnson. The genealogical blood quantum would be (bq(fe)+bq(lf))/2, but true blood quantum is just bq(lf)/2. Or take Dale Gribble and his cheating wife Nancy. She had sex with John Redcorn, so genealogical bq=0 while true blood quantum is bq(jr)/2. However, Joseph Gribble
looks Indian so I am sure he will get no trouble getting Indian benefits such as affirmative action and Indian scholarships at college.
If it's someone who is not applying for tribal membership and is instead relying on family legend (at least partially backed up by the newspaper clip in this thread in the case of Warren) you let them have their family history.
Even if it gives then professional (I understand we disagree on that, but she DID put "American Indian" on her bar registration) and political benefits (Warren used the story of her parents' supposed "forbidden love" when running for Senate)?
In any case, when Warren was at Harvard, genetic testing to establish heritage (not paternity but heritage) was not available. Today, it is not necessarily the last word or even a good indicator for some groups.
Didn't stop Harvard from touting her as "female professor of color".