Eventually Environmental Influences Will Be Demystified
As matters stand, the environment is routinely treated by many social scientists as almost mystically complicated.[38] I will have more speculative comments to make about that assumption in the next chapter, but this much is not speculative: Being freed from the restriction to samples of twins will enable this position to be explored as well, though the process will take much longer than answering the basic questions.
Is socioeconomic environment in a specific culture the issue? We don’t need to go out and assemble new longitudinal databases. We already have many large longitudinal databases with detailed data on family structure, parenting practices, SES, education, labor market experience, and just about every other interesting variable you can name. The samples for many of these databases could easily be genotyped. Take, for example, the 1979 and 1997 cohorts of the National Longitudinal Survey of Youth, two of the most widely used American databases. Almost all of the members of those samples are still alive and most of their whereabouts are known. Ask them for cheek swabs in return for the kind of genomic information for which 23andMe charges a few hundred dollars. We may be genotyping people at age 60, but in doing so we get virtually the same baseline information that we would have gotten had we genotyped them at birth.39 If we want to explore intergenerational effects, we can genotype the parents and the offspring of the members of these samples.
Are we interested in G×E interactions for ancestral populations? Every major ancestral population lives in every conceivable kind of environment. They live in countries in different parts of the world. Within most of those countries, they have varying socioeconomic status, varying numbers of generations of acculturation, and, for that matter, varying degrees of admixture with other ancestral populations. They live in countries that they rule and countries in which they are minorities. As minorities, they live in countries where discrimination against their ethnic group is severe and countries where it is negligible. Do ethnicity and environment interact in complex ways? The natural variation in the environments where ancestral populations live is so great that the raw material for answering that question is plentiful.
If the environment really is as pervasive and subtle a force as so many believe, the comparisons of polygenic scores and phenotypic scores will reveal their complex interactions and be a rich source of information for future research. But it’s also possible that for some traits in some populations in some situations, the role of the environment is not particularly complicated or important. That too would be an important finding.
Recapitulation
The great debate will not end soon. The contending parties can continue to make their respective cases on the core issues no matter what the other side says. If proving causation at the molecular level is the goal, the Turkheimer school’s pessimism seems well founded. If predictive validity is the goal, the Plomin school has good evidence that usable polygenic scores for many traits are either already available or coming soon.
I will add, however, my own view that one important issue has already been decided: There’s no longer any question whether the use of polygenic scores will be widespread. This is already obvious in medical research. In 2010, two technical articles in the U.S. National Library of Medicine contained the phrase “polygenic score” or “polygenic risk score” in the title or abstract. By 2015, that number was up to 47. In 2018, it was 171. Publications during the first half of 2019 were on pace to increase by another third.40 We can expect the same swift upsurge of publications in the social sciences.
Beyond any of the specifics I have discussed, I share Plomin’s belief that we are in the midst of an unfolding and historic revolution in the social sciences. As he put it in Blueprint, “The most exciting aspect of polygenic scores is the potential they offer for completely new and unexpected directions for research.”41 He gives examples from his own research involving schools and social mobility, but his enthusiasm is properly open-ended. When a scientific discipline gets a major new tool such as the microscope, electrolysis, or spectroscopy, the eventual uses sprawl far beyond their original ones. Polygenic scores will be a similarly multipurpose tool for expanding the questions that social scientists can ask. Ultimately, the incorporation of genetic information into the social sciences will be transformative.
15
Reflections and Speculations
The study of human diversity fascinates me, and I hope it has captured your interest as well. Ongoing discoveries in genetics and neuroscience are going to change our world in profound ways over the coming decades. I am optimistic that almost all of them will be for the better.
The findings I have presented boil down to just three cautious conclusions:
Human beings can be biologically classified into groups by sex and by ancestral population. Like most biological classifications, these groups have fuzzy edges. This complicates things analytically, but no more than that.
Many phenotypic differences in personality, abilities, and social behavior that we observe between the sexes, among ancestral populations, and among social classes have a biological component.
Growing knowledge about human diversity will inevitably shape the future of the social sciences.
I hope this long and winding account has also made it clear that we need not fear talking about human differences. Nothing we are going to learn will diminish our common humanity. Nothing we learn will justify rank-ordering human groups from superior to inferior—the bundles of qualities that make us human are far too complicated for that. Nothing we learn will lend itself to genetic determinism. We live our lives with an abundance of unpredictability, both genetic and environmental.
Above all, nothing we learn will threaten human equality properly understood. I like the way Steven Pinker put it: “Equality is not the empirical claim that all groups of humans are interchangeable; it is the moral principle that individuals should not be judged or constrained by the average properties of their group.”1
My conclusions are so cautious that they shouldn’t be controversial. If the preceding chapters haven’t persuaded you of that, a summing up in this chapter is not going to do the job.
I use this final chapter for another purpose. Writing Human Diversity has touched on topics that I have been researching and thinking about for decades. The experience has prompted many reactions on my part that don’t belong in the previous chapters because they are based on the totality of my experience. I want to express them, but I do so with trepidation. Remember that you are reading my personal and sometimes idiosyncratic interpretations. They neither augment nor diminish the empirical case for the ten propositions. The evidence that those propositions are true needs to be confronted. Having done that, go ahead and form your own opinion of their implications without regard to anything that follows. I am about to go beyond the data.
The Role of Genes in Explaining Human Differences Has Been Misconceived
It’s About More Than Traits. It’s About Human Nature.
I hope that the twenty-first century will see both social scientists and policymakers come to peace with the reality of human nature. It’s about time.
The Eclipse of Human Nature
From antiquity through the Renaissance, most thinkers took it for granted that human beings come into the world with preexisting characteristics. In the West, little was written about how people could be changed except through Christian salvation. Then toward the end of the seventeenth century came John Locke, intellectual father of the Enlightenment, who popularized the theory of the mind as blank slate—tabula rasa.2 Locke himself was advocating empiricism and opposing the use of supposedly innate ideas that justified the divine right of kings, hereditary aristocracies, and authoritarian religious institutions.3 But the blank slate metaphor was powerful. It soon spread to the assumption that human beings are malleable, molded by events and capable of being molded by design.
In the eighteenth century, this position was most flamboyantly
proclaimed by the Enlightenment’s rock star, Jean-Jacques Rousseau, who was romantically optimistic about education’s potential to do the molding by design. Even unromantic Adam Smith believed in a partially blank slate: “The difference between the most dissimilar characters, between a philosopher and a common street porter, for example, seems to arise not so much from nature, as from habit, custom, and education.”4
But Smith also had a fully realized conception of an inborn human nature (see The Theory of Moral Sentiments), and thereby represents a competing stream of eighteenth-century thought in which he was joined by others in the Scottish Enlightenment and by the American founders. Whereas the French First Republic reified the belief that humans could be molded into any shape that rational planners might devise, the American Constitution reified the belief that human nature must shape the structure of government, not the other way around. Why did the founders insist upon the checks and balances? “It may be a reflection on human nature,” Madison famously wrote, “that such devices should be necessary to control the abuses of government. But what is government itself, but the greatest of all reflections on human nature?”5
During the nineteenth century, unsentimental realism about human nature lost ground to a strange mix of idealism and rationalism that pursued extravagant goals. Karl Marx outdid all the rest with his grand theoretical application of the scientific method (as Marx saw it) to human malleability, blending history, sociology, economics, and politics into a utopian vision of what could be accomplished given the right economic and institutional structures.
The Communists who came to power in Russia didn’t think it was just theory; they thought it would work miracles. “Communist life will not be formed blindly, like coral islands, but will be built consciously, will be tested by thought, will be directed and corrected,” Leon Trotsky wrote in 1924. “Man, who will learn how to move rivers and mountains, how to build peoples’ palaces on the peaks of Mont Blanc and at the bottom of the Atlantic, will not only be able to add to his own life richness, brilliancy and intensity, but also a dynamic quality of the highest degree.”6
Elsewhere, the pioneers of the new discipline of sociology had less extreme ambitions, but they drew from the same optimism about the power of the scientific method applied to human behavior. “Our main objective,” Émile Durkheim wrote of sociology, “is to extend the scope of scientific rationalism to cover human behavior.” Causes and effects could be spelled out, he continued, and they in turn “can then be transformed into rules of action for the future.”7 The constraints of inborn human nature? “These individual natures are merely the indeterminate material that the social factor molds and transforms.”8
At the beginning of the twentieth century, the application of the scientific method to human malleability was extended to another new discipline, psychology. Behaviorism, founded by John B. Watson, took the blank slate to its ultimate expression.9
Give me a dozen healthy infants, well-formed, and my own specified world to bring them up in and I’ll guarantee to take any one at random and train him to become any type of specialist I might select—doctor, lawyer, artist, merchant-chief, and yes, even beggar-man and thief, regardless of his talents, penchants, tendencies, abilities, vocations, and race of his ancestors.10
By the 1940s, behaviorism had become a major field within academic psychology departments, with B. F. Skinner acquiring considerable fame for, among other things, his Skinner box for studying operant conditioning.11 Skinner was also convinced that you often didn’t need to study humans to understand humans—pigeons and rats would do. Or as one of his former students, Richard Herrnstein, answered, deadpan, when I asked him why behaviorists used pigeons for research: “Given the right reinforcement schedule, pigeons are indistinguishable from Harvard sophomores.”12
Eventually, the malleability assumption spilled over into policy. The social democratic left in Europe and liberal thinkers in the United States did not aspire to create a “new man” as the Communists had, but they were confident that many of society’s problems of poverty, crime, and educational failure were waiting to be solved by rational thinking scientifically applied to malleable human beings. The phrase “social engineering” came into vogue—not used sarcastically as it usually is today, but as a label for policies that would move society closer to utopia. The designers of those programs did not spend time brooding over inborn, intractable characteristics of human beings that might foil their plans.
The mid-1960s through the mid-1970s saw the apogee of American academic optimism for using public policy to change behaviors on a grand scale. But as the evaluations came in, it became apparent that the multibillion-dollar initiatives of the Great Society in education, employment, and criminal justice had not worked out as planned.13 Aspirations were scaled back. The emphasis changed from an upbeat attitude that “smart social policy can fix that!” to the darker mentality of intersectionality. By the 1990s, the problems of poverty, crime, and educational failure were increasingly ascribed to an intractable, pervasive structure of oppression.
Meanwhile, the psychologists you met in Part III were using twin studies to explore the heritability of human traits. But even those who were comfortable with a major role for heritability of discrete traits were not necessarily comfortable with a role for human nature.
Human nature refers to a coherent conception of the ways that human beings have been shaped by evolution. My idea here goes all the way back to chapter 1 and my reasons for wanting to aggregate effect sizes rather than treat them separately. What makes the differences between male and female personalities interesting and important is not an effect size of +0.24 on one facet in a personality inventory and –0.38 on another, but the way that differences on a dozen facets fit together as a profile. So it is with human nature: The important thing is not the heritabilities of specific traits but the way that the heritability of a variety of linked traits forms an interpretable mosaic.
Even psychologists who are leading scholars of heritability shy away from putting the pieces together or acknowledging that the pieces can be put together—such is the shadow that has become associated with human nature. In Steven Pinker’s words, “To acknowledge human nature, many think, is to endorse racism, sexism, war, greed, genocide, nihilism, reactionary politics, and neglect of children and the disadvantaged. Any claim that the mind has an innate organization strikes people not as a hypothesis that might be incorrect but as a thought it is immoral to think.”14 That description, written near the turn of the new century, still applies two decades later. Changing it requires a rediscovery of human nature.
The Rediscovery of Human Nature
The rediscovery of human nature has been the province of evolutionary psychology. One of my predictions about the genomics revolution, too speculative to be included in chapter 14, is that evolutionary psychology will finally take its rightful role as a major tool for understanding differences in cognitive repertoires across the sexes, ancestral populations, and social classes. One of the ways it will do so is by tying the elements of cognitive repertoires into a coherent description of human nature.
What we know as evolutionary psychology was anticipated in Darwin’s own work, but it was not until 1964 and 1972 that seminal articles by William Hamilton and Robert Trivers respectively provided a rich set of hypotheses for exploring how human nature has been shaped through evolutionary processes.15 Biologist E. O. Wilson expanded upon their work in Sociobiology (1975), and Richard Dawkins popularized some of the key themes in The Selfish Gene a year later.16 Over the course of the 1980s, psychologist Leda Cosmides and anthropologist John Tooby wrote a series of articles on evolutionary psychology that culminated in 1992 with “The Psychological Foundations of Culture,” which proposed to replace what they called the Standard Social Science Model (the intellectual version of the orthodoxy) with an Integrated Causal Model that would bring biology into the picture.17
Even as evolutionary psychology matured as a discipline and developed ways
of dealing with the dangers of just-so storytelling, it was no secret that the underlying objections to evolutionary psychology were political—the virulently hostile reaction to E. O. Wilson’s Sociobiology left no doubt about it. A familiar figure from Part II, Richard Lewontin, was joined by neurobiologist Steven Rose and psychologist Leon Kamin as authors of a denunciation of evolutionary psychology titled Not in Our Genes: Biology, Ideology, and Human Nature (1984).18 That hostility continues to this day. It is an integral part of the orthodoxy.19
Evolutionary psychologists have been fighting back for decades and can claim to have won on points many times over, but it has done little good.20 One of them, Steve Stewart-Williams, has not repressed his frustration. “Critics who rail against status quo bolstering, genetic determinism, and just-so story-telling are like the crazy person in the bus shelter, fighting with a sparring partner who isn’t really there. They’ve invented their own evolutionary psychology and are arguing loudly with that,” he wrote.21 “Fighting the evolutionary psychologists’ corner is like weeding a garden, or cutting the head off a hydra. It’s like a Nietzschean eternal recurrence, or pushing Sisyphus’s rock up the hill again and again, forever. And it’s also a pain in the butt.”22
I may sound naïve in predicting that the genomics revolution is going to finally get the rock to the top of the hill. The orthodoxy has not had a problem brushing off hard evidence in the past. Why should the genomics revolution pose a greater problem?
The reason goes back to the antiscientific bulwark that the orthodox are huddling behind. Evolutionary psychology is about the reality of inborn human nature: the role that biology has played in shaping human beings above the neck. The orthodox are saying that it’s all socialization. They have felt able to continue to maintain this position because there has not been an ironclad, you-can’t-get-around-this-one refutation of it. Polygenic scores will eventually provide that.
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