Ancestry testing on crack

Gene ExpressionBy Razib KhanApr 12, 2006 5:16 AM


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There's a terrifying article in The New York Times titled Seeking Ancestry in DNA Ties Uncovered by Tests. Here is a sample:

Alan Moldawer's adopted twins, Matt and Andrew, had always thought of themselves as white. But when it came time for them to apply to college last year, Mr. Moldawer thought it might be worth investigating the origins of their slightly tan-tinted skin, with a new DNA kit that he had heard could determine an individual's genetic ancestry. The results, designating the boys 9 percent Native American and 11 percent northern African, arrived too late for the admissions process. But Mr. Moldawer, a business executive in Silver Spring, Md., says they could be useful in obtaining financial aid. "Naturally when you're applying to college you're looking at how your genetic status might help you," said Mr. Moldawer, who knows that the twins' birth parents are white, but has little information about their extended family. "I have three kids going now, and you can bet that any advantage we can take we will."

The fact is,

most human beings are stupid, and some of them are really stupid

. And, there's money to be made here. Our society is schizophrenic about race, so no surprise that science isn't solving the problem, it is exacerbating it. On the one hand, we take Richard Lewontin's "85% variation on a locus within a race" as "proving" that race doesn't exist (statistical geneticist A.W.F. Edwards points out the problem [PDF] with this nugget of conventional wisdom), and on the other hand we go on about white skin privilege and promote policies to remediate the social impact of race in the past and the present. Race is a social reality, but it is grounded in the perception of biological differences, so the emergence of these "ancestry tests" was going to inevitably be swept into the vortex. Science and human social systems are fundamentally different. I agree with mathematical geneticist Neil Risch that many populations can be easily distinguished given enough loci. Just like the sample of salient phenotypic characters can give you a gestalt perception of an individual's ethnic origin,^1 so the enormous set of loci offered up by modern genomic techniques allows us to refine our ability to map underlying population substructure. Nevertheless, these are statistical truths, and the law is predicated on deterministic heuristics.^2 I believe this bias derives from the fact that we are natural Platonists, our minds are geared toward generating idealized protoypes and exemplars of particular categories. Our statistical inference intutions are very rough and ready, and problems like the law of small numbers or the gross inability to intuit Bayesian expectations point to the fact that even if we reflectively acknowledge graded continuity and nuanced variation across distributions, our minds will always shunt us toward discrete pebbles of preconception. We are now hurtling into the postgenomic era and within 10 years we might have affordable personalized sequencing at our fingertips. What are we going to do with this information? How are we going to swim our way through the sea of correlations and conditional probabilities which will be thrown our way? This is only an appetizers for the main course, ancestry testing is small potatos. When the "kits" start to get functional as well as ancestral, then it will be like a crack + PCP + angel dust + fucked up heroine cocktail. Pray. 1 - If I told you my skin was brown you really couldn't judge my race too well. What if I told you that my hair was straight? That would probably eliminate the sample of possibilities. What if I told you that I lacked an epicanthic fold and that my cheekbones weren't high? The possibilities are narrowing even more. Same with genes. 2 - When I say the truths are statistical, I am not saying that the error in ascertainment of whether someone is from Ghana or Sweden is very high, and in fact, it is operationally deterministic (just as visual inspection is usually not clouded by ambiguity on this issue). The problem is that just because the two ends of this spectrum are clear and distinct does not negate the fact that there are populations in the middle whose gene frequencies bridge the chasm. For example, the US Census defines Middle Easterners as white, even though a minority of Egyptians have enough Nubian admixture to "pass" for African American. The problem is that the law has to draw a hard line around categories, while modern genetics is elucidating statistical truths which exist in a cloud of probability distributions which must be framed and contextualized. In short, law is based on language, while the new genomics drinks speaks in the tongue of mathematics.

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