We are delighted Professor Sheldon Krimsky agreed to engage in a fruitful debate with us. While we appreciate his candid critique, we respectfully disagree with some of his claims and offer a defense and clarification of the views we expressed in our initial essay.
Professor Krimsky expressed concern over our characterization of heritability. There is no doubt that the concept of heritability is often the root source of much confusion. And Professor Krimsky rightly points out aspects that are generally true about heritability — including the fact that’s it’s a component of trait variance (one reflecting the role of genetic differences in human variation) and that it can change depending on environmental circumstances. Heritability is not written in stone (nor does it mean the same thing as “inherited”). We concur fully on these points, which is why we did not suggest anything different in our first essay (though we disagree that things like the equal environments assumption are very problematic, in practice). The reason we brought up heritability is because— while it is all of the things that our colleague suggests it is — it is also, as Gregory Cochran reminds us, an essential part of something called the breeder’s equation. When Cochran says, “This is the workhorse equation for quantitative genetics,” he is not exaggerating.
We should have been more careful to specify that we were referring to “additive” or “narrow-sense” heritability. But nonetheless, Professor Krimsky, in our opinion, is too dismissive of heritability. It is not simply a statistic for capturing trait variation. It’s also essential to understanding which traits are likely to “breed true” (thus, the breeder’s equation) in a population of individuals who mate non-randomly with each other. Which means, the breeder’s equation applies to people, just like it applies to any other animal. And the narrow-sense heritability of a trait helps us understand why family members resemble each other for a host of traits. If heritability were irrelevant, then no breeding program in the world would be possible, and many of our most cherished animal companions and food sources would not exist.
Professor Krimsky rightly says that “the challenge for society is where the moral boundary is or should be between selecting embryos by screening (a practice currently acceptable) and genetically engineering embryos or gametes.”
We believe that while the boundary is not always clear, the moral criteria for selecting from a set of embryos, or engineering particular embryos, are clear: the welfare of the mother, the welfare of the child that the embryo will become, and the welfare of future people who share the planet with the person the embryo will become.
Let’s take an example. Suppose we could identify a large cluster of genes that predispose people toward sadism or psychopathy. Now suppose we could choose from a set of embryos, some of which have these genes, and others of which lack them, or that we could take an existing embryo that had these genes and delete them in a safe way. We argue that parents should create children in a way that minimizes the chance that these genes find their way into future bodies. We are not arguing that government should have any role directly in these decisions, in the same way that government has nothing to say about how patients deal with hard medical decisions daily around the country (and around the world).
Since embryos lack moral standing we have little problem advancing the view that some should be selected, while others should be discarded (albeit in a respectful way, to the extent that embryos symbolize human beings with moral rights but do not actually possess moral rights). Even if embryos had moral standing, surely the loss to the embryo of an opportunity to live as a sadist or psychopath is outweighed by the gains to the future person (who begins as an embryo) who is then less likely to live an impoverished life, or undermine the lives of other people. This is an easy case, though we are willing to extend the argument to cover other forms of disability that significantly impair a future person’s chances of living a flourishing life.
Once born, severely disabled people should be respected, protected, and cared for, while also being empowered to live the most fulfilled and productive life they can. But respect for the living does not entail that we should produce disabled children, if it is in our power to avoid disability. Disabilities we might wish to avoid passing on to children include a poorly functioning immune system, an unusually high susceptibility to cancer, extreme bone fragility, exceptionally low intelligence and impulse control, or a severely attenuated capacity for empathy.
Of course, our understanding of genetics is still limited, and the technology for genetically altering embryos is not yet widely available. Even when it becomes available, it is unlikely to be safe to use in the near future. But CRISPR CAS-9 makes possibilities like these foreseeable options in the not-too-distant future.
We share Professor Krimsky’s view that intelligence is not all that matters (we said precisely this when we mentioned William Shockley’s overly-simplistic proposal to pay parents with low intelligence not to reproduce and pay parents with high intelligence to reproduce). As we argued, many qualities matter in addition to intelligence – including empathy, impulse control, creativity, and physical health. These are the kinds of general qualities we think responsible parents should want to ensure for their children, since they are the kinds of qualities that enable people to flourish, regardless of the shape their particular lives end up taking.
Professor Krimsky argues that parental licensing exams, or limits on reproduction, “can never be justified in a democratic society where having children is a basic right.” We again disagree, as do many bioethicists. For example, Dan Brock, former member of the US Presidential Bioethics Commission, has argued that while there is a defeasible right to reproduce, our reproductive choices are morally constrained by the interests of future people, including our own children, and the children they can potentially harm, or the social interests they might undermine.  John Rawls agrees, arguing that anyone who thinks about the welfare of future people should “insure for their descendants the best genetic endowment (assuming their own to be fixed). The pursuit of reasonable policies in this regard,” Rawls argues, “is something that earlier generations owe to later ones.”
While reasonable people may reject an obligation to try to shape entire future populations, everyone should accept that our individual reproductive rights are limited by our ability to take care of our children. To take an extreme case, Hugh LaFollete wryly observes “A man does not have a right to father 500 children just so he can be recognized in the Guinness Book of World Records.” We do not wish to convince readers simply by appealing to consensus, but we think it is worth noting that our position is not especially radical among professional bioethicists, even if it is not universally accepted, or widely shared among laypeople.
Finally, we would like to further emphasize a point made in our previous essay: we reject the racist and classist assumptions made by some of the more crude advocates of eugenics, including Madison Grant, whose repulsive views Hitler admired and enacted. Thoughtful advocates of eugenics, including Nobel laureate Herman Muller, have long opposed racist and classist views. According to Muller —
In view of…the offensively reactionary attitude flaunted by that vociferous group of eugenicists who were actuated by race and class prejudices, it is not surprising that some three-quarters of a century of old-style eugenics propaganda has resulted in so little actual practice of eugenic principles by people in general.
As Muller (who was half Jewish and half German) understood, being a member of a racial or ethnic minority is not evidence of being undesirable. Far from it. We think diversity is desirable, and we both enjoy living in a cosmopolitan society. But we think it is better if people’s lives go as well as possible, and we agree with Professor Krimsky that we should use environmental tools like nutrition and education to improve human welfare. We just go one step farther and argue that we should also use our increasing understanding of genetics to make it more likely that certain environmental interventions will work.
Jonathan Anomaly is a Lecturer at Duke University and Research Assistant Professor at UNC Chapel Hill
Brian Boutwell is an Associate Professor of Criminology and Criminal Justice at Saint Louis University. Follow him on Twitter @fsnole1
 “Genetic Progress by Voluntarily Conducted Germinal Choice,” The Future of Man, 1963, p. 256.