On Monday, Sen. Elizabeth Warren (D-Mass.) Published DNA test results, suggesting that she has Native Americans and is putting the spotlight on genetic testing and the identity of Indians.
The DNA Report Comes Back After years of political back and forth between Warren and Republican opponents who accuse them of ostensibly having American blood to advance their legal careers. A DNA "fact check" on a political debate would have appeared before some election cycles such as science fiction. But even today, DNA descent tests are not as straightforward as it seems, especially when it comes to finding an Indian identity. [How Do DNA Ancestry Tests Really Work?]
"It's important to think about where the community and culture come from," said Matthew Anderson, a geneticist at Ohio State University, who hails from eastern Cherokee. "It's not the DNA."
What Does Of Course
Warren, who was born in Oklahoma, has long claimed that her relatives had Indian blood on her maternal side, a family history passed down from generation to generation. The new DNA test shows that Warren actually has five segments in its genome that are common to indigenous American populations. Carlos Bustamante, a Stanford University geneticist who conducted the analysis, told the Boston Globe that the results indicate that Warren had a Native American six to ten generations ago. The results seem trustworthy, said Genetics experts contacted by Live Science.
Bustamante's assessment is "enough good enough to do what he says," said J. Douglas McDonald, emeritus professor of chemistry at the University of Illinois, who developed biogeographic analysis software for descent experiments.
But Warren's findings would not qualify them to seek tribal membership. The tribes determine their own roles (list of members) and do not use DNA descent tests. Some use genealogy research and set specific requirements for the proportion of Indian blood needed for membership; Others require that applicants prove that they are related to someone who is already a member of the tribal membership.
"A DNA test is useless to determine tribal citizenship," said Cherokee Secretary of State Chuck Hoskin Jr. in a statement. "Current DNA testing does not even differentiate whether a person's ancestors were native to North or South America."
In fact, Bustamante told the Boston Globe that he had compared Warren's gene sequences to genomes from South American indigenous populations, because only such data gives a limited amount of data from North American populations. Since the indigenous peoples of South and North America have common ancestors ̵
In fact, no DNA test can clearly prove or disprove that a person has an ancestor of a particular ethnicity. The results are reported in terms of probabilities, not certainties, Anderson said. That's because of the way genes are passed on.
When you travel through your family tree in time, each relative contributes an ever smaller portion of their DNA to your genome. Each of your parents contributes about 50 percent; By the time you come to your 16 great-great-grandparents, everyone contributes only about 6.25 percent of their DNA to you. Their 64 great-great-great-great-grandparents contribute only 1.56 percent.
It's easy to imagine that if only one of these 64 great-great-great-great-great-primal Natives were Native Americans, their contribution would be hard to find the rest of your DNA, especially since commercial DNA testing does not cover the whole Genome but certain segments of it. (Various commercial tests also examine different segments of the genome, so the results of descent may vary slightly from test to test, according to Roots & Recombinant DNA, a blog of the genetic genealogist TL Dixon.)
The picture becomes even blurry because the amount of DNA delivered is not fixed. DNA strands recombine randomly when passed from semen and egg; This random rearrangement can mean that a given great-great-great-great-great-grandparent contributes even less than the theoretically assigned 1.56 percent. [Genetics by the Numbers: 10 Tantalizing Tales]
"You've inherited half of your DNA from your mother and half your DNA from your biological father," Anderson said. "That's pretty clear, but where does the DNA of your two parents come from? It's a mix of their parents … It could really be distorted into Grandparent 1 instead of Grandparent 2."
Because of this rearrangement, the genetic contribution of a known ancestor can essentially disappear or "wash out" after a few generations.
Genetic washout is especially likely when one particular ethnic group is prevented from mixing with the broader population, as it was among Indians, with the US government's policy of removing them from their land and abandoning them To isolate reservations, wrote Dixon. This means that someone could have a Native American ancestor but no genetic contribution from this ancestor in his DNA.
On the other hand, a DNA test that reveals segments that are common to Indian populations can not prove that your ancestor was original. Since the Native Americans have common ancestors with East Asians, an "Indian" genetic segment could have come from an East Asian ancestor. Again, it's about probabilities, Anderson said. The more segments you have associated with a particular ethnicity, the more likely it is that you are descended from people of that ethnic background. But since such variants occur in different populations and at different frequencies worldwide, it is difficult to say that just because you have a particular variant, they are derived from a certain population, Anderson said.
A historical policy about who "counted" as Native American also blurs the lines. Some Asian populations that immigrated to the United States in the 1700s and 1800s have landed and lived among Native Americans, and many tribal members today have genetic backgrounds full of European, African, and Asian DNA, thanks to historical blending (a genetics) term for the mixing of different populations). This may mean that people who are legally and culturally Native American have DNA with relatively few "Native American" sequences.
An example of the complications of blood and culture is the Cherokee Freedmen case, a tribal quarrel that reached the Cherokee The Supreme Court of the Nation in 2006. The Cherokee freedmen were the descendants of slaves who held by members of the Cherokee tribe. After the emancipation, these freedmen were allowed to join the Cherokee nation first. But in the 1980s, the tribe's citizenship laws changed to require a genealogical link to a tribal member listed as Blood Cherokee on the Dawes Rolls, a federal registry of Cherokee members from the early 1900s. This change deprived many freedmen of their tribal citizenship, despite the fact that they were culturally Cherokee and descended from generations of relatives who were also culturally Cherokee. The legal debate lasted until 2017, when a US district court ruled that the freedmen had rights to Cherokee citizenship and the Cherokee nation accepted the verdict.
"People forget that the people we assume are black can also be Indians, and they are completely excluded from these conversations," Anderson said.
According to the American Indian & Alaska Native Genetics Resource Center, many tribes are wary of genetic testing for their history of forced relocation and assimilation. The tribes also had intense interactions with medical researchers, as in an Arizona State University project with the Havasupai tribe of the Grand Canyon. In this case, blood samples originally collected in the late 1980s were later used for further research without the consent of the participants, resulting in litigation. Some tribes, such as the Navajo Nation, have issued moratoria on genetic research on their land. Other tribes, such as the Salt River Pima-Maricopa Indian Community, have built partnerships with researchers so they have a say in the conduct of studies. Nevertheless, data on Native American DNA according to Dixon remain relatively sparse compared to other groups.
The advent of commercial genetic testing has flooded the offices of many tribal agencies with applications based solely on DNA results, Anderson said. While many early tests overestimate probabilities based on small amounts of provenance, McDonald said today's Ancestry.com tests seem to do a better job and avoid false results. However accurate the tests may be, they can not determine the identity of Native Americans.
"In which communities are you part of, which stories do you have, which traditions have you retained?" He said. "Those are the things that define who you are, more than the fraction of your genome."
Originally published on Live Science .