,
18 tweets,
10 min read
Read on Twitter
Woke up to the dubious honor of a namecheck in @WSJ. @FreemanWSJ uses my reporting to back the false assertion that @SenWarren's Native American ancestry is no different than that of average European Americans. For those interested in facts, a thread 1/ wsj.com/articles/did-e…
Yesterday @senwarren released an analysis of her DNA that revealed five segments of DNA containing genetic markers indicating they originated in the people who first came to the Americas. I wrote about it for @nytimes nytimes.com/2018/10/15/sci… 2/
Based on the segment sizes, geneticist @cdbustamante & his colleagues estimated @senwarren has a Native American ancestor who lived 6-10 generations ago. @FreemanWSJ concludes—wrongly—that Warren is between “1/64th and 1/1024th” Native American (i.e.,1.56%-.097%). Mistake #1! 3/
Geneticists like @CDBustamante measure ancestry in terms of the percentage of a genome that they can assign to ancestral populations. You can’t pretend that every ancestor in a generation contributed an equal amount of DNA to you, as if DNA is a pie you cut into equal slices. 4/
From generation to generation, some DNA from ancestors fails to transmit. When a woman produces an egg, for example, it randomly grabs one copy of each chromosome. More of her mother’s chromosomes may end up in the egg than her fathers. 5/
Over time, more DNA gets lost. @grahamcoop & colleagues have calculated the odds that one of your ancestors transmitted NO DNA AT ALL to you. Here’s his figure. (I write about this in more detail in “She Has Her Mother’s Laugh” bit.ly/SheHasHerMothe… ) 6/ 
Then @FreemanWSJ makes his 2nd error. He quotes from my 2014 @nytimes story about a @23andMe study. They compared people’s who self-identify as African American, European American, or Latino. It's fascinating, so it’s annoying to see it misrepresented nytimes.com/2014/12/25/sci… 7/
Looking at 160,000 customers, the @23andMe team determined—among many other things—that their European American customers on average have .18% Native American ancestry. 8/
So @FreemanWSJ takes his erroneous 1.56%-.097% figure for @senwarren and then wrongly combines it with the .18% figure from the other study, and declares, “her genetic makeup is perhaps similar to that of the average white person in the U.S.” 9/
This is the same rhetorical tactic deployed by a GOP spokesman yesterday, by the way. They’re both wrong 10/ 10/
For starters, the .18% average requires unpacking to avoid the wrong impression. It doesn’t mean if any European American you pick at random will have ~.18% Native American DNA. Actually, the vast majority of self-identified European Americans have NO Native American ancestry 11/
Here’s a graph from the 2014 paper w/Native American ancestry of the 3 self-described groups. Red bars show almost all Europeans have zero ancestry. Less than 1% have 2% ancestry. European Americans with more Native American ancestry are even rarer. cell.com/ajhg/fulltext/… 12/
Another mistake @FreemanWSJ makes is mixing apples and oranges These two studies rely on different methods to get DNA data and analyzing it. To compare @senwarren to @23andMe’s customers, you'd have to use their technology and software. 13/
As @razibkhan tweeted yesterday, Warren would likely end up with a relatively high estimate in such a test. 14/
Here’s 1 reason we know that. @cdbustamante compared @senwarren’s DNA to the genomes of 183 people of European descent who live in Utah and England. Warren’s NA segments are 10-12 times longer than the NA-like segments in those people. 15/
The tiny segments in the people from Utah and England have likely been floating around in human populations for tens of thousands of years. Warren’s much longer DNA segments, on the other hand, must have come from a much more recent recent Native American ancestor 16/
I wish that op-ed pieces could be fact-checked, but I guess that’s too much of a dream, eh? Anyway—teachers, if this looks like a teachable moment about ancestry, Native American identity, etc., please look to folks like @grahamcoop and @KimTallBear for accurate guidance. 17/END
