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SKEPTOID BLOG:

Can Your DNA Tell You Your Ancestry?

by Stephen Propatier

August 18, 2015

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Donate For those of us living in the United States there's a cottage industry for ancestry determination. For a fee, websites like ancestry.com or familytree.com claim to research your family history. I have long been fascinated by these advertisements. I always thought it unlikely that a website could accurately track down my family tree without physically researching it. Still, it is possible that they could have a vast database of computerized immigration records. Recently, there have been advertisements purporting the use of DNA testing to tell you your "true" ancestry. DNA testing, unlike a family tree, is a well developed science. Is this feasible? Can your DNA tell you your ancestry? If so how? Since DNA is in the realm of science, I think taking a look at it skeptically is worthwhile.

America is almost exclusively a nation of immigrants. And from an even broader skeptical viewpoint, ties to any real estate are really just a question of squatters' semantics, meaning that if you go back far enough we all originated from the same area of the world.We are pretty sure that at some point in the distant past there was less than 18,000 humans in Europe, Africa and Asia. That "bottleneck" in history probably means that we are all more closely related than anyone really realizes. Our genetics is a road map that extends back through time to the earliest forms of life. It is arbitrary to select one time out of that genetic history and mark that as your heritage.

Nonetheless, people like to have a sense of continuity about their past, and share a cultural heritage. Because the US is relatively young as a nation, I think we have an overdeveloped sense of heritage. While heritage for Americans is just as important as it to other nationalities, the average US citizen has a relatively short family history, and they tend to identify with the families country of origin, using hyphenated labels like Irish-American, African-American, Italian-American, etc.

As perplexing as it is to some visitors to the United States, Americans' tendency to hyphenate their nationality is typically a way of talking about their cultural heritage. Yet the term nationality is often used. A good example of this is my own foolish thinking when I was a young man, and some amusement I probably provided to a customs official in Great Britain 20 years ago, when I was 18 years old, on a class trip to London. The security measures for customs and the airlines were very different at the time. On final approach we were handed applications for a tourist visa to Great Britain. One of the card's questions concerned nationality and I put "Portuguese" as my response. It sounds ridiculous to someone outside of the US, but when my family talked about nationality we were Portuguese. Both sides of my family immigrated to the US about 70 years ago, from the Azores, and some of my family members only spoke Portuguese. So it seemed reasonable to me at the time to give that answer. As you may have guessed the customs agent in Heathrow airport sighed, looked at me, and asked some questions that confused me at first, then soon made me feel silly. He asked "What language do you speak?" to which I answered "English." Then he asked "Where is your passport from?" My answer (becoming more confused) was "The United States." He then proceeded to say "Just so you know, you're an Amer-ri-can, not Portuguese." I was very embarrassed. Today I find the whole episode amusing, and a good example of how insular thinking can affect your perception. For those of you outside the US, it is a good example of how confusing ancestry and heritage can be in American culture.

Can a DNA test clear up questions you may have about your heritage? If so how? In television advertisements, these companies show a person who talks about his family's German ancestry, how devout he was towards his family traditions including lederhosen dancing (Schuhplattler). But when he learns that his DNA indicates his ancestry is Scottish rather than German, he eagerly replaces his lederhosen with a Scottish tartan kilt.

There are many problems here for me. I am certain that this is a stylized advertisement—not an actual person. But family traditions like lederhosen dancing exist apart from a DNA test. Culture is learned and has nothing to do with your genetics. The whole idea that someone can learn who they really are through genetics is, in my opinion, nonsense. I find the whole idea that DNA markers are a superior method to determine ancestry slightly racist, similar to the idea that "blood" is paramount. Furthermore, I agree with a 2007 article in the journal Science, about ancestry DNA testing, in which the authors write:
"Because race has such profound social, political and economic consequences, we should be wary of allowing the concept to be redefined in a way that obscures its historical roots and disconnects from its cultural and socioeconomic context. The article recommends that the American Society of Human Genetics and other genetic and anthropological associations develop policy statements that make clear the limitations and potential dangers of genetic ancestry testing. Among the potentially problematic byproducts of widespread genetic ancestry testing: questionable claims of membership to Native American tribes for financial or other benefits; patients asking doctors to take ancestry tests into consideration when making medical decisions; and skewed census data due to people changing ethnicity on government forms. Moreover, many Americans are emotionally invested in finding an ancestral homeland, and thus vulnerable to a test that can produce mixed results at best and false leads at worse. 'This search for a homeland is particularly poignant for African Americans, who hope to recapture a history stolen by slavery.'"
All of the major companies advertising this form of ancestry-related DNA testing use autosomal DNA tests. The companies don't exactly promote the accuracy of the test, but tend to give the impression that it is the path to your true heritage. It takes a little searching, but you can find a disclosure that accurately shows the companies' beliefs about the usefulness of their tests. For example, ancestry.com writes:
"Your AncestryDNA results include information about your ethnicity across 26 regions/ethnicities and identifies potential relatives through DNA matching to others who have taken the AncestryDNA test. Your results are a great starting point for more family history research, ?and it can also be a way to dig even deeper into the research you've already done."
That is a far less rosy answer than the advertising leads you to believe. Admixture DNA testing is a valid test—not a sham—but the results are complicated and very limited. It examines non-sex chromosomes inherited from both parents and identifies chromosomes that contain DNA segments from all ancestors. To a limited extent, this test can track the geographical movements of ancestors by examining single nucleotide polymorphisms (SNPs), some of which influence traits such as skin color and resistance to regional diseases. Using that information there are patterns of human genetic diversity which could be weakly correlated with racial and ethnic categories. Those are, in turn, partially correlated with geography. However the same SNPs may be found among several populations around the world, and thus can produce false leads. The companies use the ancestry markers to show genetic differences between what are assumed to be four biologically distinct populations: Africans, Europeans, East Asians, and Native Americans.

Even the language shows some major flaws for this type of test—i.e. weakly correlated, partially correlated, and assumed-distinct populations. And this isn't the only problem in using these tests for discovering ancestry. The results rely on a database of samples to correlate these findings. You need a comparison to a known DNA marker to know that your genetic markers are associated with a certain region. Genetic matching depends largely on the number of samples in a company's database. The researchers published in Science wrote:
"Even databases with 10,000 to 20,000 samples may fail to capture the full array of human genetic diversity in a particular population or region.
The team also pointed out that research into this type of testing has shown inherent flaws, with the writers noting:
"Dark-skinned East Africans might be omitted from the AIMS reference panel of 'Africans' because they exhibit different gene variants."
This means that a certain sizable African populations (the most genetically diverse region on the planet) may not fit in the African marker group, despite being from Africa, appearing to share the same outward traits as other Africans in the database, and having a shared cultural heritage. Such a risk of failure makes this test dubious.

Others have have rolled out mitochondrial DNA testing, which is more problematic. Because such tests analyze less than 1 percent of a person's genome, they will miss most of a person's relatives. If you take a mitochondrial DNA test, you learn something about your mother's ancestry. It leaves out completely your father's ancestry. Plus, if you go back as little as 10 generations, that test is telling you something about only one ancestor out of more than a thousand from that part of your family tree.

Overall DNA tests fail because they cannot account for recent migrations of peoples from their ancient homelands. Present-day patterns of residence are rarely identical to what existed in the past, and social groups have changed over time, in both name and composition. The relation between genetic and cultural heritage is unbelievably murky given current world wide mixing of populations. And, as noted before, these tests don't actually tell you anything about who you are. If you're adopted by an Italian family, raised from birth as Italian, and will die believing you're Italian, how does a DNA test change that? What right does a DNA test have to steal your legacy and tell your great, great, great grandchildren that they are in fact Swedish? None at all. Ancestry is a legacy, not a bloodline.

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You can follow me at Twitter @steveproacnp for a daily dose of skeptical nursing. Please check out the completion of the series Occ: The Skeptical Caveman, which I helped produce with the guys at The Skeptics Guide To the Universe.

Disclaimer: This post is my personal opinion, it is not a substitute for medical care. It is for informational purposes only. The information on Skeptoid blog is not intended nor recommended as a substitute for medical advice, diagnosis, or treatment. Always seek the advice of your own physician or other qualified health care professional regarding any medical questions or conditions. This post does not reflect the opinion of my partners, professional affiliates, or academic affiliations. I have no financial conflicts of interest to disclose.

by Stephen Propatier

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