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Senator Elizabeth Warren (D-Mass.) Released the DNA test results on Monday, suggesting that she was originally Native American and that she was putting the issue of genetic testing and genetic testing at the forefront. Native American identity.
The DNA report comes after years of political clashes between Warren and Republican opponents, who accuse him of pretending to have Native American blood to advance his legal career. A "factual control" of DNA on a political debate would have seemed like science fiction, even there are some electoral cycles. Even today, however, DNA ancestry tests are not as simple as it seems, especially when it comes to looking for an Amerindian identity. [How Do DNA Ancestry Tests Really Work?]
"It's important to think about the origins of community and culture," said Matthew Anderson, a geneticist from Ohio State University, originally from eastern Cherokee. "This is not the DNA."
What does indigenous mean
Warren, born in Oklahoma, has long argued that his maternal parents had Native American blood, a family story passed down from generation to generation. The new DNA test shows that Warren actually has five segments in his genome that are common to Native American populations. Carlos Bustamante, a geneticist from Stanford University who performed the analysis, told the Boston Globe that the results indicate that Warren had a Native American ancestor six to ten generations ago. The results seem reliable, said experts in genetics contacted by Live Science.
The evaluation of Bustamante is "satisfying enough to do what he says," said J. Douglas McDonald, Emeritus Professor of Chemistry at the University of Illinois, who developed a biogeographic analysis software for testing Pedigree.
But Warren's results would not qualify her to become a member of a tribe. Tribes determine their own lists (membership list) and do not use DNA progeny to do so. Some use genealogy research and set some requirements for the percentage of Native American blood needed to become a member; others require that applicants prove that they are related to a person already on the list of members of a tribe.
"A DNA test is useless for determining tribal citizenship," said Chuck Hoskin Jr., Cherokee Nation Secretary of State, in a statement. "Current DNA testing does not even allow us to determine whether a person's ancestors were indigenous to North or South America."
Indeed, Bustamante told the Boston Globe that he had compared Warren's gene sequences to genetic segments of indigenous populations in South America because available data on Native American populations North were limited. Because the indigenous peoples of South America and North America share common ancestors – a population that probably crossed the Bering Strait at least 15,000 years ago – they also have more genetic sequences in common only with people of European descent. But this information is far too unspecific for the test to attribute the ancestor of a person to a certain tribe. [In Photos: Human Skeleton Sheds Light on First Americans]
Complicated genes
In fact, no DNA test can conclusively prove or disprove a person with an ancestor of a specific ethnicity. The results are reported in terms of probabilities, not certainties, Anderson said. This is because of the way the genes are transmitted.
As you step back in time in your family tree, each member of your family is contributing a smaller and smaller portion of their DNA to your genome. Each of your parents contributes about 50%; By the time you arrive at your great-great-great-grandparents, each one is only reporting 6.25% of his DNA. Your 64 great-great-great-great grandparents contribute only 1.56% each.
It is easy to imagine that if only one of these 64 great-great-great-great-grandparents were Native American, their contribution could be difficult to find among the rest of your DNA, especially since commercial tests of DNA does not detect the entire genome but rather some segments of it. (Different commercial tests also select different segments of the genome, which is why pedigree results may differ slightly from one test to another, according to Roots & Recombinant DNA, a blog written by the genetic genealogist TL Dixon.)
The situation becomes even more blurred because the amount of DNA transmitted is not fixed. Strands of DNA recombine randomly when they are transmitted from a sperm and an egg; This random rehandling may mean that a given great-great-great-great-great-great-grandparent contributes even less than the 1.56% that is theoretically attributed to him. [Genetics by the Numbers: 10 Tantalizing Tales]
"You inherited from your biological father half of your DNA from your mother and the other from your biological father," Anderson said. "It's pretty clear, but where does your parents' DNA come from? It's a mix of their parents. … That could be really skewed towards Grandparent 1 instead of Grandparent 2. "
Because of this reshuffle, the genetic contribution of a known ancestor can essentially disappear, or "disappear" after a few generations.
Genetic leaching becomes especially likely when a specific ethnic group is prevented from mixing with the wider population, as was the case for Native Americans, thanks to the US government's policy of expelling them from their lands and to isolate them on the reserves, Dixon wrote. This means that one might have a Native American ancestor, but no genetic contribution from that ancestor in his DNA.
Framework
On the other hand, a DNA test that reveals segments common to Amerindian populations can not prove that your ancestor was aboriginal. Because Native Americans share common ancestors with East Asians, a "Native American" genetic segment could come from an ancestor in East Asia. Again, it's all about probabilities, Anderson said. Generally, the more segments you have associated with a specific ethnic group, the more likely you are to descend from people of that ethnic group. But as such variants appear worldwide, in different populations and at different frequencies, "it's hard to say that just because you have a specific variant, you're inherently derived from a certain population," he said. said Anderson.
The historical policies on which "counted" as Native American also scramble the lines. Some Asian immigrant populations in the United States between the 1700s and 1800s ended up living among Native Americans, and many tribal members now have a genetic background filled with European, African and Asian DNA, thanks to a historical mix (a term for mixing different populations). This may mean that legally and culturally Amerindian people have DNA with relatively few "Native American" sequences.
The case of Cherokee Freedmen, a dispute over tribal affiliation that culminated in the Supreme Court of the Cherokee Nation in 2006, is an example of the complications of blood and culture. The Cherokee Freedmen were the descendants of slaves owned by members of the Cherokee tribe. After the emancipation, these free men were first allowed to join the Cherokee Nation. But in the 1980s, tribal citizenship laws were amended to impose a genealogical link to a tribe member listed as Cherokee by blood in Dawes Rolls, a federal government list composed of early-dating Cherokee members of the XXth century. This change deprived many men of their tribal citizenship, despite the fact that they were culturally Cherokee and descended from generations of parents also culturally Cherokee. The legal debate lasted until 2017, when a US District Court ruled that the Freedmen were entitled to Cherokee citizenship and that the Cherokee Nation had accepted the decision.
"People forget that the people we suppose blacks can also be Native Americans, and they are totally excluded from these conversations," Anderson said.
Many tribes are wary of genetic testing because of their history of forced resettlement and assimilation, according to the Native Genetics Resource Center of Native Americans, Alaska and Alaska. The tribes also had many interactions with medical researchers, as part of a project of Arizona State University with the Grand Canyon Havasupai tribe. In this case, blood samples taken in the late 1980s were then used for other research projects without the consent of the participants, resulting in legal action. Some tribes, such as the Navajo Nation, have imposed moratoriums on genetic research on their lands. Other tribes, like the Indian community Pima-Maricopa Salt River, have formed partnerships with researchers to enable them to participate in the conduct of studies. Nevertheless, according to Dixon, the DNA data of Native Americans remain relatively rare compared to other groups.
The advent of commercial genetic testing has flooded the offices of many tribal authorities with applications based solely on the results of DNA, Anderson said. Although many early tests overestimated the odds on the basis of a few ancestors, McDonald said, the current tests of An Ancestry.com seem to be more effective in avoiding false results. However accurate, the tests can not define the Native American identity.
"What communities do you belong to, what stories do you have, what traditions have you maintained," he said. "These are the things that define who you are, more than the fraction of the genome you have."
Originally published on Science live.
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