Have we leapt into commercial genetic testing without understanding it?

Source: Ars Technica

An “Adversarial Collaboration”

Trejo is a quantitative sociologist at Princeton; Martschenko is a qualitative bioethicist at Stanford. He is a he, she is a she; he looks white, she looks Black; he’s East‑Coast, she’s West‑Coast. On the surface, it seems clear that they would hold different opinions. Yet they spent ten years writing this book together in an adversarial collaboration. While they still disagree, they have learned to truly listen to and understand each other—a worthwhile achievement in today’s world.

The titular “What We Inherit” refers both to actual DNA (Trejo’s field) and to the myths surrounding it (Martschenko’s). The authors focus on two pervasive “genetic myths.”

1. The Destiny Myth

The notion, first promulgated by Francis Galton in his 1869 book Heredity and Genius, that the effects of DNA can be separated from the effects of environment. Galton did not deny nurture; he erroneously pitted it against nature, treating them as mutually exclusive rather than inter‑dependent. (In his worldview, the most powerful “genetic” determinant of educational attainment was a Y chromosome.) His ideas culminated in the forced sterilizations of the eugenics movement in early‑20th‑century America and later in the policies of Nazi Germany.

2. The Race Myth

The false belief that DNA differences divide humans into discrete, biologically distinct racial groups. While humans can be genetically sorted by ancestry, this is not the same as defining rigid racial categories.

The bulk of the book discusses polygenic scores, which aggregate the impact of many small genetic influences. The authors cover:

• What polygenic scores are
• Their strengths and weaknesses
• Their historical development, current applications, and future potential
• How—and how much—their use should be regulated

Ultimately, they ask: Are polygenic scores worth generating and studying at all?

Science Education

Both authors agree that science education in the United States is abysmal and needs immediate improvement. Most people’s understanding of genetics is stuck at Mendel’s classic experiments—dominant vs. recessive traits illustrated with green vs. yellow, smooth vs. wrinkled peas and Punnett squares. In reality, most human traits are far more complex, especially the interesting ones.

Polygenic Scores: Uses and Abuses

Polygenic scores tally the contributions of many genes to particular traits in order to predict certain outcomes. There’s no single gene for height, depression, or heart disease; instead, a multitude of genes each make very small contributions, making an outcome more or less likely.

Polygenic scores cannot tell you that someone will drop out of high school or earn a PhD; they can only indicate that someone might be slightly more or less likely to do so. They are probabilistic, not deterministic, because mental health, educational attainment, and even height are shaped by both environmental factors and genetics.

Limitations

1. Accuracy – By nature, polygenic scores are not highly accurate.
2. Trait trade‑offs – Accuracy declines when you try to select for more than one trait (e.g., height and intelligence).
3. Ancestry bias – Scores are less accurate for individuals who are not of European descent, since most genetic studies to date have been conducted on European populations.

Consequently, any potential benefits of this technology will be distributed unevenly from the outset.

Calls for Regulation

Martschenko and Trejo argue that the generation, sale, and use of polygenic scores must be regulated far more assiduously than they currently are to ensure responsible and equitable implementation. They write:

“While scientists and policymakers are guarding the front gate against gene editing, genetic embryo selection (using polygenic scores) is slipping in through the backdoor.”

Potential parents using IVF have long been able to choose embryos based on gender and clear‑cut genetic markers for serious diseases. Now they can also choose embryos based on polygenic scores.

Commercial Offerings

• Genomic Prediction (2020) – Offered scores for diabetes, skin cancer, high blood pressure, elevated cholesterol, intellectual disability, and “idiopathic short stature.” The last two were later removed “because it’s too controversial,” not because the effects are minor or the science unreliable.

  • The theoretical maximum polygenic score for height would shift stature by about 2.5 inches, a difference not yet observed even in European cohorts.
  • Scores for most other traits lag far behind.

• Herasight – Claims to provide embryo‑selection services based on intelligence, filling the gap left by other companies.

Practical Considerations

• Trait selection trade‑offs – The more traits you try to select for, the less accurate each prediction becomes.
• Pleiotropy – Many genes influence multiple biological processes; a gene linked to an undesirable trait may have undefined effects on desirable ones.
• Environmental impact – Ignoring the child’s environment can lead to overestimating the benefit of genetic selection. For example, the first couple who used genetic screening for their daughter chose an embryo with a <1 % reduced risk of heart disease. Simple lifestyle interventions (e.g., encouraging vegetable consumption and sports participation) would have been cheaper and likely more impactful.

In summary, while polygenic scores hold promise, their current limitations, ancestry bias, and the ethical complexities of embryo selection demand careful regulation and a balanced view of genetics versus environment.

The Risks of Reduced Genetic Diversity

Almost every family I know has a child who has taken growth hormones, and many also use tutoring. These interventions are far from equitably distributed. If embryos are selected based on polygenic scores, a new form of social inequality could arise. While growth‑hormone injections affect only one individual, embryonic selection based on polygenic scores influences that embryo’s descendants for generations. The chosen embryos’ progeny could eventually be treated as a new class of “optimized” people whose elevated status stems simply from parents who could afford to comb through 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 they find objectionable would make humanity more uniform and society poorer for the loss of heterogeneity. Everyone benefits from exposure to people who are different. If everyone were bred to be tall, smart, and good‑looking, how would we learn to tolerate otherness?

The Atlantic – “The Last Children of Down Syndrome”

Current Legal Landscape

• United Kingdom, Israel, and much of Europe: Polygenic embryo selection is illegal.
• United States (2024): The FDA has signaled intent to regulate the market, but for now companies offering polygenic scores to the public are treated like nutritional supplements—non‑medical and therefore not regulatable.

These companies market scores for traits such as musical ability and acrophobia, claiming “wellness” or “educational” purposes.

Societal Implications

• Corporate control: Americans are largely at the mercy of private firms that profit from these services while claiming to help consumers.
• Economic disparity: Wealthy individuals—often with European ancestry—are the only ones who can afford to pursue genetic advantages for their children, reinforcing existing social inequalities and potentially creating new genetic stratifications.
• Future accessibility: If the “snake‑oil” phase eventually yields reliable polygenic scores, the hope is that they will become inexpensive enough for anyone who wants them.

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