Is Human Agency in Danger of Being Drowned by Genetic Determinism?
Erik Parens, PhD is a Senior Research Scholar at The Hastings Center and director of its Initiative in Bioethics and the Humanities.
In his new book, Understanding the Nature-Nurture Debate, Eric Turkheimer sums up much of his thinking over his long and distinguished record as a behavioral geneticist. As a scientist, he has sought to understand what twin, adoption, and family studies can—and cannot—show regarding the role of genes in the emergence of human behavior. As a thinker, he has sought to understand what findings from those studies do—and do not—mean for us as individuals, who experience ourselves as having agency, and as citizens, who are acutely aware of the injustice and inequality that plague our society. And, as a colleague, Turkheimer has shown unstinting generosity to those of us in bioethics who want to understand what the science shows and what it means.
As the Human Genome Project took off in the 1990s and 2000s, Turkheimer had the insight and courage to stand nearly alone among his colleagues in criticizing what he took to be their unrealistic enthusiasm about how useful it would be—in terms of improving both behavioral and medical care—to sequence human genomes. He was among the first to recognize the way in which discoveries of single “genes for” rare disorders like cystic fibrosis were, essentially, red herrings in the hunt for causal pathways from genes to common disorders and other complex traits. Had Turkheimer’s skepticism about discovering causal pathways been taken more seriously, those charged with caring about the public’s health might have adjusted how much they invested in genomics.
But it isn’t such practical implications that preoccupy him in the new book. Rather, it is the ethical and social ones. Specifically, for most of the book, he focuses on defending the reality of subjective experience in general, and of human agency in particular, against what he worries could become a flood of genetic determinism. As someone who shares the ethical and social commitments that he seeks to protect, I want to suggest where his defense is leaky, and gesture at a more straightforward way of resisting the implications that worry him most.
The heritability of divorce
In the new book, Turkheimer explains that a 1992 paper on the genetics of divorce had a profound effect on him. The paper reported results consistent with the suggestion that divorce is substantially “heritable.”
That effect on Turkheimer was not because he was surprised that divorce is heritable. On the contrary, the year before he had, in a commentary with his mentor Irving Gottesman, announced the “first law of behavioral genetics,” according to which, virtually all human characteristics are, to use the behavioral geneticists’ term of art, heritable. As Turkheimer and Gottesman said, to observe that all human characteristics are heritable simply means that, “some of the variance of every human characteristic is influenced by genes” (ital. in original). That is, if you want to explain observed differences in a population with respect to any human characteristic, some of that variation will be attributable to genetic differences. Or, as we might put it more colloquially, genes have “something to do” with why individuals show up in the world differently: not just how tall we are or how much we weigh, not just how prone we are to hypertension or to getting cancer, but how empathic we are, how prone we are to become distracted, and how quick we are to anger. And yes, God help us, how we perform on standardized intelligence tests.
When Turkheimer and Gottesman wrote their commentary, their observations were based on insights from twin studies that started being done in the 1970s. Those studies calculated “heritability coefficients,” which, in the simplest case, were based on the fact that identical twins share 100% of their genes and fraternal twins share about 50% of theirs, and on the assumption that the environments of identical and fraternal twins are equally similar. Basically, the more concordant identical twins are on a given trait than fraternal twins are, the greater the heritability coefficient, and the greater the genetic influence that is inferred.
In their commentary about the heritability of virtually all human traits, Turkheimer and Gottesman were surely not suggesting that those traits are “inherited” or “genetically determined.” Rather, they were telling those environmentalists who spoke as if genes had nothing to do with complex traits, that it was time to recognize that they did. And they were telling the geneticists that it was no longer necessary to do more studies to demonstrate that genes have something to do with observed variations. How could it be otherwise? Each of us, after all, emerges from a single cell, a large part of which is genes. The way he puts it in the new book: to say that genes have “something to do with” variation in all human characteristics is “tautological.”
The troubling conclusion
So why did that 1992 paper on the genetics of divorce have such a profound effect on him? Right after mentioning it, he identifies, in the form of a question, the “the troubling conclusion” that he feared many listeners would reach: “Was it now time to embark on studies of genetic mechanisms that underlie failing marriages, and give up on understanding them at the psychological level of the couples’ therapist?” (ital. added). His fear was that, upon hearing that divorce is heritable, listeners might conclude that divorce is inherited or genetically determined, and that rather than try to understand divorce at “the psychological level of experience,” we should try to understand it in terms of genetic mechanisms. He worries that, rather than attempting to intervene at the level of subjective experience with environmental interventions like marriage counseling, we would imagine it would soon be possible to intervene at the level of genes.
The idea that divorce is heritable does not precipitate just one troubling conclusion, but several. Most generally, he worries that, if we were to believe that the heritability of traits entails that they are genetically determined, we would give up understanding ourselves as free agents capable of moral behavior. And, if we believed that the inequality that plagues our society is the result of the aggregated behaviors that are determined by genes, we would abandon hope of reducing that inequality with environmental interventions. Ultimately, Turkheimer is defending against the Ur troubling conclusion: that the father of eugenics and great grandfather of behavioral genetics, Francis Galton, was right, and the inequality that characterized Victorian England was just a reflection of the way nature is.
More specifically, what deeply concerns Turkheimer is that a belief in genetic determinism can be used to shore up racist fantasies about the putative genetic superiority of whites over Blacks with respect to intelligence. (Different from many other progressives who are horrified by the political agenda of our contemporary Galtonites, Turkheimer does not reject the claim that intelligence is among the most valid and reliable of psychological constructs.) For decades he has taken deadly seriously the putrid history of claims by people like Arthur Jensen, Richard Herrnstein, and Charles Murray, who in the second half of the 20th Century “hypothesized” that the genetic influence on intelligence was so large that we might as well think of it as genetically determined, and that, given the Black-white gap in educational achievement, attempts to narrow the gap with environmental interventions like better schools were doomed to fail. And Turkheimer takes with equal seriousness, and has equal contempt for, those on the alt-right today who relentlessly circulate variations on that same hateful and unproved—and with current science unproveable—claim.
What troubles Turkheimer almost as much as the ravings of those obsessed with making comparisons between groups, are the less incendiary claims made by those in the behavioral genetics mainstream today, who focus on differences within groups. An especially irksome example of the latter is Robert Plomin, whose book with the eminently clickable title Blueprint: How DNA Makes Us Who We Are, can certainly sound like he believes that all human characteristics, including intelligence, are genetically determined.
Two ways out of the troubling conclusions
Immediately after articulating the troubling conclusion—that divorce is genetically determined and therefore there’s little value in understanding marital discord at the level of subjective experience—he identifies what he calls two “ways out.” The first is to dismiss all of behavioral genetics on methodological grounds. (For example, one objection is to the behavioral geneticists’ assumption that identical and fraternal twins inhabit equally similar environments. If the environments of identical twins are more similar than the environments of fraternal twins, geneticists are overstating the extent to which the greater concordance between identical twins on observed traits is due to genetics.) Although many critics have taken that way out, Turkheimer rejects it. He takes the evidence for the meaningfulness of the heritability concept to be too strong.
But, he says, “There is another way out, which is ultimately what this book is about” (ital. added). Basically, the book aims to protect us from genetic determinism, and to establish, once and for all, that to say that a trait or outcome (e.g., divorce) is heritable, is not to say that it is genetically determined.
On the one hand, one might think that defending that claim hardly requires a book. After all, insofar as heritability coefficients are ultimately ratios, meant to indicate how much of the observed variation in a population is due to genetic variation and how much is due to environmental variation, it should be obvious that complex traits are not influenced by genes alone. On the other, there is that putrid history—and present—of claims like the one that the heritability of intelligence explains both why our current social order looks the way it does and why trying to change it won’t work.
So what is Turkheimer’s way out of the troubling conclusions?
Unknown and unknowable causal events
His way out is to remind us that heritability coefficients are based on correlations, and to argue that the “demonstrable causal events underlying those correlations, …, are mostly unknown and unknowable” (ital. added). That is, his way out is to establish that we are, and shall forever remain, mostly ignorant of the genetic mechanisms involved in, or the causal pathways that lead from genes to, human behaviors.
When he says that the genetic mechanisms and causal pathways are unknown, he is stating a simple fact. The psychologists who did those early twin studies—long before the molecular techniques associated with the Human Genome Project came online—could, of course, not point to genetic mechanisms. Although those old-fashioned studies did allow researchers to infer that genes had “something to do with” observed differences, they couldn’t say anything about which genes were involved or how they were.
As above, when the molecular techniques came online, there was great enthusiasm about the imminent discovery of genetic mechanisms. Yet almost all of those efforts—whether linkage studies, candidate-gene studies, or genome-wide association studies—turned out, largely, to be a bust. (Polygenic indexes, about which there is enthusiasm today, are like heritability coefficients in that they do not purport to identify genetic mechanisms.) Although molecular techniques have in some cases been used to illuminate “patches” of those causal pathways from genes to behaviors, it is fair for Turkheimer to emphasize that they remain unknown.
It is, however, when Turkheimer says those processes are unknowable that his analysis runs into trouble.
Unknowable, in practice, vs. unknowable, in principle
Most of the time when he says that the mechanisms are unknowable he means that, in practice, ethical barriers will keep us from doing the sorts of breeding experiments that he says would allow us to know them. (I leave it to geneticists to say whether future molecular techniques will obviate the need for the sort of breeding experiments that he assumes would be necessary.)
But he also uses unknowable in a very different sense. As a non-religious scientist, he says explicitly that he has no patience for appeals to the sort of “extra-physical souls” that have been invoked in the past by those who want to carve out a space where science can’t reach. Nonetheless, he flirts with the claim that the mechanisms that give rise to human behaviors are, in principle, unknowable, in the sense of being beyond the ken of the sciences.
We can see him flirt with that claim at the start of his first chapter, where he offers a surprisingly extended exegesis of the first three chapters of the Book of Genesis. In Genesis he finds a conception of a “dualistic relationship” between humans and the rest of nature that he sees as helpful. The first thought he finds there is easy to reconcile with Darwin: insofar as human beings are, like the rest of creation, made of dust, we are part of, or unified with, nature. But the second thought can’t be reconciled with Darwin: insofar as humans have dominion over the rest of nature, we are exiled, or separate, or distinct from nature. As he says at the end of his exegesis: “The punishment for our knowledge of good and evil, the only thing about us the theory of evolution can’t take away, is to be exiled forever from nature” (ital. added). That is, the one thing that distinguishes us from the other animals and that Darwin can’t take away—and that is beyond the ken of the sciences—is our capacity for moral behavior.
Later in the chapter, Turkheimer returns to why the mechanisms undergirding our behaviors are unknowable:
"[W]e do not experiment on humans because we believe (whether in a religious or secular sense) that humans are sacred; we believe humans are sacred because, in our experience, we exist outside the deterministic domain of natural science" (ital. added).
Notice that in the first part of that sentence, he is alluding to the ethical barriers to experimenting on humans, and thus to the first sense in which genetic mechanisms will remain unknowable. But in the second part of that sentence, he flirts with the second sense: those mechanisms will remain unknowable because our behaviors are “beyond” or “outside” the domain of natural science. I say “flirts with” because he does not explicitly say that humans are outside the deterministic domain of natural science. He says that “in our experience” we are.
Then, immediately after flirting with the thought that genetic mechanisms are unknowable, he says why we should leave those mechanisms unknown:
"Humans remain outside that domain because we can’t – mustn’t – create the inhuman conditions that might show otherwise. We can either maintain a special proto-scientific place for human freedom and morality, or we can pursue human science to its carnivorous, fascist, deterministic end; we can’t have both" (ital. added).
That is, he has moved from flirting with the claim that genetic mechanisms are unknowable because humans are outside the domain of science, to the claim that we should not do research that “might show” that we are inside it. He has moved from the dualistic claim that we cannot understand human behavior in scientific terms because it occurs outside the domain of science, to the strategic claim that we should not try to understand human behavior in scientific terms because doing so would mean giving up on conceiving of ourselves as capable of moral behavior and would lead to genetic determinism and worse.
The dualistic move
In the final chapter he restates what he calls “the paradox at heart of the human condition”:
“We are animals, full stop. Yet we are not.”
Specifically, he suggests here that we are not animals insofar as we have the “ability to have goals and react to inborn qualities and the vicissitudes of the environment by modifying those goals and optimizing the actions we take to reach them.”
But as many a biologically-minded philosopher, like Hans Jonas, and many a philosophically-minded biologist, like Kevin Mitchell, have argued, having and modifying goals does not make us different in kind from the rest of the animals. We can glimpse the beginning of having goals already in amoebas, not to mention in dogs and elephants and chimpanzees. In this view, even the amoeba is not a passive, stimulus-response machine, but a metabolizing organism, which, to survive, must actively “interpret” the meaning of the information in its environment. Yes, of course, there are gigantic differences between non-human and human animals. But the difference is not that, whereas science can explain the behaviors of non-human animals, it, in principle, cannot explain the behavior of humans.
To believe that human behavior is beyond the ken of science requires some sort of substance dualism, in which humans are constituted by material bodies, which are within the ken of science, and by immaterial minds, which are beyond it. It requires the sort of extra-physical mind that Turkheimer knows he should not—and says he does not want to—appeal to.
An alternative to the dualistic move
I have (without any originality) argued elsewhere that we do not need to invoke extra-physical, disembodied minds to escape the conclusion that Turkheimer worries would follow from believing that outcomes like divorce can be explained in terms of genetic mechanisms. That is, we don’t need to appeal to anything extra-natural to protect the reality of our subjective experience. Instead of flirting with the idea that our behaviors are unknowable because our minds are beyond the ken of science, we can accept a couple of facts and take a more pragmatic approach.
The first fact is that we are natural objects like all the others in this world. This means that our behaviors are, at least, in principle, explainable in terms of genetic and environmental determinants. Notice: this entails that genetic determinism is plainly false, insofar as environmental determinants (including epigenetic determinants and chance), too, help to explain why we behave the way we do.
But rejecting genetic determinism does not entail rejecting determinism—in the weak sense that all natural phenomena have causes, and where, by definition, “genetic” and “environmental” cover all of the causes found in nature. Accepting a weak form of determinism allows for recognizing that within the network of causes of our current behaviors, are, for example, memories of the consequences of our past behaviors. To accept that it is, in principle, possible to explain human behaviors without appealing to extra-natural causes, does not entail explaining away lived experience in the way that “hard” determinists are wont to do.
The second fact, the one that Turkheimer is concerned we will lose sight of if we give genes too much credit, is that we are also subjects. As he is keen to remind us, there is something that it is like to be each of us. Indeed, our own subjective experience is unique to our particular form of embodiment and place in the world. If I want to know what it is like for you to be you, I need to ask you. In the moment I am trying to understand what you are saying, I am not trying to explain why you are saying it.
As Turkheimer says, it would be terrible if anyone imagined, based on the fact of heritability coefficients, that looking to genetic mechanisms would be the way to repair marriages. Partners in marriage counseling need to try to understand what it is like for each to be the other. They need to see, and be seen by, the other as a subject.
But in his effort to emphasize that fact, he seems to forget that the effort to understand what it is like for the other can—if done at the right time and in the right way—be complemented by trying to explain why they are having the experience they are having. It can sometimes be enormously helpful to notice that our behaviors and experiences have myriad causes, from genes being expressed and neurotransmitters being transmitted, to childhood memories being sparked and internalized sexism or racism or classism being triggered.
More concretely, if someone brings to their marriage a trait like impulsiveness or neuroticism or substance abuse, recognizing that those behaviors have causes can sometimes help to modulate them. Maybe medication, or meditation, or exercise, or a different job can help one or both partners. To that extent, seeing ourselves as objects need not be dehumanizing. On the contrary, few behaviors are more fully human than being able to oscillate between seeing ourselves as objects and as subjects.
The strategic move
As I mentioned above, it is not only his dualistic move to defeat genetic determinism that I think is unhelpful. I also find it hard to go with him when he shifts to making the strategic move of cautioning against trying to discover such causal pathways and genetic mechanisms on the grounds that they “might show” that we are inside the domain of science.
When he makes that move he seems to allow that, if we started rooting around in the domain of science looking for genetic causes, we might find them. As above, there is no prospect that fills him with as much dread as the day when—different from today—it is scientifically possible to use genetics to make comparisons between groups with respect to performance on intelligence tests.
Indeed, it seems it is that ethical concern about between-group comparisons that is especially important in motivating his persistent minimizing of the meaningfulness of the scientific idea that genetic differences have “something to do” with observed differences within groups. He couldn’t be clearer about that motivation than when he writes, “Anyone who is ready to believe that you are smarter than me because your genes make you smarter also has to explain whether groups of people like you are smarter than groups of people like me for the same reason.” But important ethical arguments aren’t helped by weak scientific claims. And the suggestion that, in general, genetic differences do not have something to do with observed differences within groups is scientifically weak.
Turkheimer is keenly aware that his emphasis on how little heritability coefficients tell us, and on how little it means to say that genes have something to do with observed differences, may be frustrating to some readers. As he says, in his “constant minimizing of the implications of heritability,” he can seem like he is trying to keep his “finger in the dike against an inevitable onslaught of … genetic determinism… and the apotheosis of Galton’s proclamation … that ‘a man’s natural abilities are derived by inheritance, under exactly the same limitations as are the form and physical features of the whole organic world.’”
Begrudgingly, the “i” word appears
An important part of keeping his finger in that dike against genetic determinism is to avoid, throughout most of the book, saying that genes “influence” behavior (even though in the original, 1991 statement of the first law, he and Gottesman said that “some of the variance of every human characteristic is influenced by genes” [third ital. added]). But then, in the final chapter, it’s no longer possible to avoid the “i” word. That’s because he wants to introduce a conception of the role of genes that is superior to the one the gene hunters assumed back in the 1990s and 2000s. In what the developmental biologists call the process of “canalization,” the word influence is central, and to introduce their understanding of that process Turkheimer uses the example of divorce:
"At each step in the process [of human development], from early cellular divisions to the reaction when jilted in 10th grade, genes have their thumb on the scale. At every choice point, whether right or left, up or down, towards domestic bliss or divorce court, the outcome is influenced – intentionally using the vague causal word—by some set of genes" (ital. added).
Here we have the sober view that Turkheimer offers at the very end and very beginning of the book: genes don’t determine traits, but they play a role in all of the developmental processes that lead to observable traits. It’s just that for most of the book it can sound like he has a different view. For most of it, in his effort to keep his finger in the dike against the onslaught of genetic determinism and the troubling conclusions, he can sound like he rejects the idea that genes exert an influence.
Coda
Absolutely none of this is to gainsay the insight and courage it took for Turkheimer to resist the original genetic enthusiasts who, upon learning that all human characteristics are heritable, imagined that it soon would be possible to discover causal pathways from genes to complex traits. The practical implications remain large.
But in his effort to resist the negative ethical and social implications of misunderstanding what heritability means, he too often exaggerates the insignificance of learning that genetic differences have something to do with observed differences. That effort unfortunately entails his flirtation with the sort of substance dualism that anyone who wants to think clearly about genes and behavior needs to get over. It’s just not helpful to accept the picture in which “physical” characteristics are tied to material bodies and “behavioral” characteristics are tied to immaterial minds, which are, in principle, unknowable by the natural and social sciences.
It is time, I think, for those of us who share Turkheimer’s ethical and social commitments, to adjust course. To start, we need to remember the value of oscillating between seeing ourselves as objects whose behaviors can, in principle, be explained, and as subjects whose experiences demand to be understood. And we need to remember that when we see ourselves as objects, we don’t need to spend precious energy defending against the patently false claim that human behavior is genetically determined. Instead, we can start spending even more energy than Turkheimer already does in broadcasting the fact that, the more that contemporary genomics researchers study the role of genes in the emergence of human traits, the more they appreciate the importance of environmental determinants—and the more they recognize how exceedingly difficult it is, in practice, to specify the mindbogglingly complex mechanisms by which genetic and environmental determinants give rise to human behavior. None of that requires us to minimize the fact that genes have something to do with why we all show up in the world differently. And it surely doesn’t require us to abandon our efforts to understand behavior at the level of psychological experience.
