When Elizabeth Warren released her DNA results last week, indicating a Native American ancestor a few generations back, my response was, and still is, so what?
Besides the facts that the revelation wasn’t surprising, its interpretation insulting to Native Americans, and in many accounts oversimplified or flat out incorrect, to challenge a presidential taunt (“Pocahontas”) is a waste of ATP. One of my own articles was even bumped last Tuesday, replaced with a piece claiming that “almost every American has a sliver of Native American ancestry.”
No, it’s not that simple.
But the main reason I didn’t drop everything to pontificate about Senator Warren’s relative along with the other quoted geneticists of the day is because it hit too close to home. I’m immersed in a DNA ancestry journey myself, an unexpected one that began recently when Ancestry.com discovered a close relative I didn’t know I had. And that person is just about my age – not someone from 7 generations ago.
I’m still collecting information, trying to imagine a narrative that makes sense. The memories and possibilities are coming to me slowly, as I read about other older adults whose histories may have to be tweaked in the wake of findings from direct-to-consumer DNA tests. My story will be too long for a blog post so I have to figure out where to publish it, if I publish it.
Right now, my mind is a scorecard, with reasons why the finding can’t be true on the left, yet the actual data, on the right, too statistically convincing given what I know about DNA genomes to dismiss.
As I search for answers, and inspired by the overreaction to Senator Warren’s teensy-by-comparison DNA finding, I thought it might be helpful to list some of the estimates, approximations, assumptions, and inferences that DNA ancestry testing entails. The ads are so sappy that I fear people may assume that spitting in the tube and popping it into the mail generates a genome sequence.
No, it’s not that complex.
Instead, deeming two people relatives with DNA testing is like identifying a book from a few distinctive phrases or sentences. The book is the generic genome, the signature phrases what testing actually reveals two people share.
Google “What in the Sam Hill he’s doing?” and it might not indicate much, but add “That boy’s yo’ comp’ny and if he wants to eat up the tablecloth you let him, you hear?” and a scene from To Kill a Mockingbird emerges. Scout is shocked at her friend pouring maple syrup over his dinner, when cook Calpurnia pulls her aside and explains. An incomplete scene, an incomplete genome, holds less meaning than the full story.
Still, my newfound relative and I share an uncanny number of specific DNA stretches. But most of our genomes weren’t even analyzed. Here are some of the shortcuts:
- Ancestry testing to match relatives considers less than .02% of the genome, in the form of 700,000 or so SNPs (single nucleotide polymorphisms) and not always all four DNA base possibilities at each site. That’s 700,000 out of 3.2 billion bits of DNA information.
- The algorithm that spits out cousins, aunts, and grandparents is trained on pairs of people who are related in known ways, like aunt/uncle to niece/nephew or first cousins. It’s searching for a machine-learned pattern.
- Also considered are the frequencies of short DNA sequences in populations around the world. But not all populations have been analyzed, and companies’ databases may disagree or be proprietary.
- The pie charts of geographical origins assume that grandparents and relatives farther back didn’t move around much. Like assuming most of us have a smidgeon of Native American DNA, that simply wasn’t always true.
The larger lesson: DNA testing, of any kind and especially direct-to-consumer, is serious. Not entertainment. Think before you spit, because once you know something, you can’t unknow it. I wish I’d never sent samples to companies offering to test me for free if I wrote about them, years ago. After I’d learned I was 100% Ashkenazi, which I already knew, I’d forgotten all about it.
When I wrote “DNA Testing Kits as Holiday Gifts Can Bring Surprises” here last December, I had no idea it would happen to me.
The bottom line is that until a few weeks ago, I thought I knew everything there was to know about DNA testing. But I had no idea of the sucker punch that unexpected findings can deliver – even when they’re good.
Source: DNA Science.
