Have we leapt into commercial genetic testing without understanding it?
A new book argues that tests might reshape human diversity even if they don’t work.
Daphne O. Martschenko and Sam Trejo both want to make the world a better, fairer, more equitable place. But they disagree on whether studying social genomics—elucidating any potential genetic contributions to behaviors ranging from mental illnesses to educational attainment to political affiliation—can help achieve this goal.
Martschenko’s argument is largely that genetic research and data have almost always been used thus far as a justification to further entrench extant social inequalities. But we know the solutions to many of the injustices in our world—trying to lift people out of poverty, for example—and we certainly don’t need more genetic research to implement them. Trejo’s point is largely that more information is generally better than less. We can’t foresee the benefits that could come from basic research, and this research is happening anyway, whether we like it or not, so we may as well try to harness it as best we can toward good and not ill.
Obviously, they’re both right. In What We Inherit: How New Technologies and Old Myths Are Shaping Our Genomic Future, we get to see how their collaboration can shed light on our rapidly advancing genetic capabilities.
An “adversarial collaboration”
Trejo is a (quantitative) sociologist at Princeton; Martschenko is a (qualitative) bioethicist at Stanford. He’s a he, and she’s a she; he looks white, she looks black; he’s East Coast, she’s West. On the surface, it seems clear that they would hold different opinions. But they still chose to spend 10 years writing this book in an “adversarial collaboration.” While they still disagree, by now at least they can really listen to and understand each other. In today’s world, that seems pretty worthwhile in and of itself.
The titular “What we inherit” refers to both actual DNA (Trejo’s field) and the myths surrounding it (Martschenko’s). There are two “genetic myths” that most concern them. One is the Destiny Myth: the notion, first promulgated by Francis Galton in his 1869 book Heredity Genius, that the effects of DNA can be separable from the effects of environment. He didn’t deny the effects of nurture; he just erroneously pitted it against nature, as if it were one versus the other instead of each impacting and working through the other. (The most powerful “genetic” determinant of educational attainment in his world was a Y chromosome.) His ideas reached their apotheosis in the forced sterilizations of the eugenics movement in the early 20th century in the US and, eventually, in the policies of Nazi Germany.
The other genetic myth the authors address is the Race Myth, “the false belief that DNA differences divide humans into discrete and biologically distinct racial groups.” (Humans can be genetically sorted by ancestry, but that’s not quite the same thing.) But they spend most of the book discussing polygenic scores, which sum up the impact of lots of small genetic influences. They cover what they are, their strengths and weaknesses, their past, present, and potential uses, and how and how much their use should be regulated. And of course, their ultimate question: Are they worth generating and studying at all?
One thing they agree on is that science education in this country is abysmal and needs to be improved immediately. Most people’s knowledge of genetics is stuck at Mendel and his green versus yellow, smooth versus wrinkled peas: dominant and recessive traits with manifestations that can be neatly traced in Punnet squares. Alas, most human traits are much more complicated than that, especially the interesting ones.
Polygenic scores: uses and abuses
Polygenic scores tally the contributions of many genes to particular traits to predict certain outcomes. There’s no single gene for height, depression, or heart disease; there are a bunch of genes that each make very small contributions to making an outcome more or less likely. Polygenic scores can’t tell you that someone will drop out of high school or get a PhD; they can just tell you that someone might be slightly more or less likely to do so. They are probabilistic, not deterministic, because people’s mental health and educational attainment and, yes, even height, are determined by environmental factors as well as genes.
Polygenic scores, besides only giving predictions, are (a) not that accurate by nature; (b) become less accurate for each trait if you select for more than one trait, like height and intelligence; and (c) are less accurate for those not of European descent, since most genetic studies have thus far been done only with Europeans. So right out of the gate, any potential benefits of the technology will be distributed unevenly.
Another thing that Martschenko and Trejo agree on is that the generation, sale, and use of polygenic scores must be regulated much more assiduously than they currently are to ensure that they are implemented responsibly and equitably. “While scientists and policymakers are guarding the front gate against gene editing, genetic embryo selection (using polygenic scores) is slipping in through the backdoor,” they write. Potential parents using IVF have long been able to choose which embryos to implant based on gender and the presence of very clearcut genetic markers for certain serious diseases. Now, they can choose which embryos they want to implant based on their polygenic scores.
In 2020, a company called Genomic Prediction started offering genomic scores for diabetes, skin cancer, high blood pressure, elevated cholesterol, intellectual disability, and “idiopathic short stature.” They’ve stopped advertising the last two “because it’s too controversial.” Not, mind you, because the effects are minor and the science is unreliable. The theoretical maximum polygenic score for height would make a difference of 2.5 inches, and that theoretical maximum has not been seen yet, even in studies of Europeans. Polygenic scores for most other traits lag far behind. (And that’s just one company; another called Herasight has since picked up the slack and claims to offer embryo selection based on intelligence.)
Remember, the more traits one selects for, the less accurate each prediction is. Moreover, many genes affect multiple biological processes, so a gene implicated in one undesirable trait may have as yet undefined impacts on other desirable ones.
And all of this is ignoring the potential impact of the child’s environment. The first couple who used genetic screening for their daughter opted for an embryo that had a reduced risk of developing heart disease; her risk was less than 1 percent lower than the three embryos they rejected. Feeding her vegetables and sticking her on a soccer team would have been cheaper and probably more impactful.
The risks of reduced genetic diversity
Almost every family I know has a kid who has taken growth hormones, and plenty of them get tutoring, too. These interventions are hardly equitably distributed. But if embryos are selected based on polygenic scores, the authors fear that a new form of social inequality can arise. While growth hormone injections affect only one individual, embryonic selection based on polygenic scores affects all of that embryo’s descendants going forward. So the chosen embryos’ progeny could eventually end up treated as a new class of optimized people whose status might be elevated simply because their parents could afford to comb through their embryonic genomes—regardless of whether their “genetic” capabilities are actually significantly different from everyone else’s.
While it is understandable that parents want to give their kids the best chance of success, eliminating traits that they find objectionable will make humanity as a whole more uniform and society as a whole poorer for the lack of heterogeneity. Everyone can benefit from exposure to people who are different from them; if everyone is bred to be tall, smart, and good-looking, how will we learn to tolerate otherness?
Polygenic embryo selection is currently illegal in the UK, Israel, and much of Europe. In 2024, the FDA made some noise about planning to regulate the market, but for now companies offering polygenic scores to the public fall under the same nonmedical category as nutritional supplements—i.e. not regulatable. These companies advertise scores for traits like musical ability and acrophobia, but only for “wellness” or “educational” purposes.
So Americans are largely at the mercy of corporations that want to profit off of them at least as much as they claim to want to help them. And because this is still in the private sector, people who have the most social and environmental advantages—wealthy people with European ancestry—are often the only ones who can afford to try to give their kids any genetic advantages that might be had, further entrenching those social inequalities and potentially creating genetic inequalities that didn’t exist before. Hopefully, these parents will just be funding the snake-oil phase of the process so that if we can ever generate enough data to make polygenic scores actually reliable at predicting anything meaningful, they will be inexpensive enough to be accessible to anyone who wants them.
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