If you're Native American, there's a good chance that you've thought a lot about blood quantum — a highly controversial measurement of the amount of "Indian blood" you have. It can affect your identity, your relationships and whether or not you — or your children — may become a citizen of your tribe.

Blood quantum was initially a system that the federal government placed onto tribes in an effort to limit their citizenship. Many Native nations, including the Navajo Nation and the Turtle Mountain Band of Chippewa Indians, still use it as part of their citizenship requirements.

And how tribes use blood quantum varies from tribe to tribe. The Navajo Nation requires a minimum of 25 percent "Navajo blood," and Turtle Mountain requires a minimum of 25 percent of any Indian blood, as long as its in combination with some Turtle Mountain.

Blood quantum minimums really restrict who can be a citizen of a tribe. If you've got 25 percent of Navajo blood — according to that tribe's blood quantum standards — and you have children with someone who has a lower blood quantum, those kids won't be able to enroll.

So why keep a system that's decreasing your tribe's rolls and could lead to its demise?

"I use the term 'Colonial Catch 22' to say that there is no clear answer, and that one way or another, people are hurt," says Elizabeth Rule. She's a doctoral candidate at Brown University who specializes in Native American studies, and also a citizen of the Chickasaw Nation.

"The systems are so complicated," she explains, "but it's all part of tribes deciding on their own terms, in their own ways, utilizing their own sovereignty [to decide] what approach is best for them."

As we explored blood quantum in this week's episode, we thought a primer of what, exactly, this system is and how it works — or doesn't — might be useful. Here's my interview with Elizabeth Rule, edited and condensed for clarity.

First of all, what's blood quantum?

Blood quantum simply is the amount of "Indian blood" that an individual possesses. The federal government, and specifically the Department of the Interior, issues what is called a "Certified Degree of Indian Blood," and that is a card similar to an ID card. So the way that blood quantum is calculated is by using tribal documents, and usually it's a tribal official or a government official that calculates it.

But really it's a mathematical equation. So the quantum is a fraction of blood that is derived going back to the original enrollees of a tribe who were counted on Census rolls, and then their blood quantum was documented, and usually those original enrollees had a full blood quantum. Typically.

How did people know that those original enrollees had "full blood quantum"?

Well, they didn't. And that's that's one of the major problems with blood quantum today is that a lot of times, the people taking the rolls were federal government officials who were unfamiliar with Native ways of establishing and defining their own communities.

And so, for example, these officials would mark someone potentially as "full blood" when potentially that person was not. And that assumption was based on their appearance, on their level of cultural involvement with their community.

But a great example for how to understand this problem in real life is that there is a history of freedmen who are black individuals who were living as fully incorporated members of Indian tribes. And when these original roles were taken, oftentimes these freedmen were not included, even though those individuals may be of mixed heritage: black and Indian. Because of their black appearance, they were listed on a separate roll. And today, the ramification is that they do not have that original enrollee [in their past]. They do not have enough blood quantum, and therefore oftentimes cannot be extended tribal membership.

Can you talk to me about how the concept of blood quantum came to be used for Native tribes?

Certainly, American Indians have been racialized. But our primary identity continues to be a political one. Blood quantum really emerges as a way to trace race between generations of Native people starting at the turn of the 20th century. And again, I think it's helpful to understand the way that blood quantum works through another example that people may be more familiar with — and that's the "one drop rule."

The one drop rule measured the amount of "black blood" that black people had in society. And that ensured that every person who had at least one drop would be considered black and would be covered under these discriminatory laws and, even in the earlier days, enslaved.

Blood quantum emerged as a way to measure "Indian-ness" through a construct of race. So that over time, Indians would literally breed themselves out and rid the federal government of their legal duties to uphold treaty obligations.

One of the questions that kept coming up is: OK, so why don't tribes just ditch these blood quantum requirements and switch to an enrollment requirement that uses lineal descent? (Lineal descent basically means that, if your ancestors were enrolled in a tribe, you can be, too.)

That is the question of the century. And first, I want to be clear that I don't intend to speak on behalf of any specific tribes or even on behalf of my own, but I'm happy to walk you through some of those arguments that exist in support of maintaining blood quantum requirements for tribal membership. ...

The thing that I've found to be most interesting about both arguments — in support and against blood quantum requirements — is the language of survival. So, lineal descendant supporters think about high memberships through the lens of existence as a resistance right. And so there's a desire to build up tribes' numbers and capacity in order to survive and perpetuate the tribe.

On the other side, those who defend blood quantum requirements also evoke this language of survival, and they look upon those blood quantum minimums as a way to preserve an already existing closed community that's very close and ... usually very culturally connected.

Even though they're using what a lot of people say is a "Colonialist construct"?

Yes. And I don't think that anyone would argue that it isn't that. That history is very clear. But, tribes today of course have to adapt, and blood quantum for some tribes in their view has been a way to preserve their community.

I also want to emphasize that it is the tribe's sovereign right to determine their own membership and whether that involves a blood quantum minimum or lineal descent system.

Ultimately their decision has to be respected in order to uphold tribal sovereignty.

You've used the phrase "personal gains" before to refer to some people who might've claimed Indian heritage. Can you walk me through what specifically those personal gains look like?

You hear every time a tribe changes over to lineal descent, or that there is a newly recognized tribe, for example, that usually there's a mass group that's interested in joining. And potentially, some of those incentives would be financial gain if the tribe, for example, has gaming revenue or other industries. Of course, there is a desire on some individuals' part to claim an identity for affirmative-action purposes. But again, I would say that is certainly the minority of this side of the cases. But it does happen and I just want to point it out again to show that there are difficulties on both sides and that there's not a clear-cut answer yet.

If each tribe is able to determine their own their own enrollment requirements, are there any tribes out there that you've heard of that are deciding to forego lineal descent and blood quantum — and deciding to use another completely different method?

I have heard of one example in Canada, where a First Nation has decided to open enrollment to people who have no Indian ancestry at all. Meaning that those individuals don't meet the federal Canadian requirements of being a "status Indian," and they also don't have that blood quantum or descendancy from an original enrollee. It's an extremely progressive and interesting move, and they're really changing the game.

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