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TL;DR - Genetic tests don't give good regional ancestry results if you are from a region that is underrepresented by genetic testing.

electricslpnsld 9y ago
That, and that gene tests are simply correlating against gene distributions from when the samples were collected, so present day. If there was a major population movement in the past fifty years (Syria to mediterranean Europe in the author's case), the results won't reflect an American-centric view of what it means to be from Syria or Italy or wherever.
m0rphling 9y ago
That's only partially true. The real issue is that there is no official representation of race or heritage found in DNA. Modern genetic testing is a best-effort exercise for classification whose 'accuracy' varies by sample size, race coverage, and group(s) sponsoring testing/analysis. Quite simply, one cannot look at a DNA sequence and say definitively it is one race or another—there is no official Rosetta Stone for translating DNA to race or heritage.
- Houshalter 9y ago
  That's not really true. If you look at just the basic PCA of genetic data, several races emerge very clearly and distinctly. E.g. look at this image: https://i.imgur.com/J2Xl2FK.png https://i.imgur.com/J2Xl2FK.png I'm just guessing here, but I think the problem is they are trying to do something more complicated than just find your nearest genetic cluster. They want to find exactly what mix you are between different clusters. It's clear on the graph that some people have more African ancestry than others. But what would be an algorithm for working out the exact percentage "African" someone is? Is it euclidean distance to the median african? Or the furthest bottom left african? Or is it just the first principle component alone? The second problem is they don't just want 7 big clusters. People already know they are European, they are more interested in exactly what countries/regions they are from. And making a bunch more clusters makes the problem more complicated.
searine 9y ago
It's also the fact that the author's family is heavily admixed. That makes assigning them to any one group precisely, a very difficult task with large margins of error.

electricslpnsld 9y ago

That, and that gene tests are simply correlating against gene distributions from when the samples were collected, so present day. If there was a major population movement in the past fifty years (Syria to mediterranean Europe in the author's case), the results won't reflect an American-centric view of what it means to be from Syria or Italy or wherever.

m0rphling 9y ago

That's only partially true. The real issue is that there is no official representation of race or heritage found in DNA. Modern genetic testing is a best-effort exercise for classification whose 'accuracy' varies by sample size, race coverage, and group(s) sponsoring testing/analysis. Quite simply, one cannot look at a DNA sequence and say definitively it is one race or another—there is no official Rosetta Stone for translating DNA to race or heritage.

Houshalter 9y ago
That's not really true. If you look at just the basic PCA of genetic data, several races emerge very clearly and distinctly. E.g. look at this image: https://i.imgur.com/J2Xl2FK.png https://i.imgur.com/J2Xl2FK.png I'm just guessing here, but I think the problem is they are trying to do something more complicated than just find your nearest genetic cluster. They want to find exactly what mix you are between different clusters. It's clear on the graph that some people have more African ancestry than others. But what would be an algorithm for working out the exact percentage "African" someone is? Is it euclidean distance to the median african? Or the furthest bottom left african? Or is it just the first principle component alone? The second problem is they don't just want 7 big clusters. People already know they are European, they are more interested in exactly what countries/regions they are from. And making a bunch more clusters makes the problem more complicated.

searine 9y ago

It's also the fact that the author's family is heavily admixed. That makes assigning them to any one group precisely, a very difficult task with large margins of error.