Dalton Conley is a professor at Princeton University. He is a member of the National Academy of Sciences and, in 2005, received the National Science Foundation’s award for best young scientist, mathematician, or engineer.
What’s the big idea?
For over 150 years, the debate over nature versus nurture has shaped how we understand human development—but pioneering scientist Dalton Conley argues this framing is all wrong. In The Social Genome, he explores the groundbreaking field of sociogenomics, which reveals how genes and environment interact to shape who we become. Using advances in molecular genetics, Conley shows how DNA influences everything from parenting styles to school performance, even shaping the nurture we receive. This provocative book offers a new perspective on human potential and the ethical challenges of a future where genetic insights could reshape education, health, and society itself.
Below, Dalton shares five key insights from his new book, The Social Genome: The New Science of Nature and Nurture. Listen to the audio version—read by Dalton himself—in the Next Big Idea App.
1. The polygenic index is the new FICO score of human biology.
When the human genome was sequenced in 2003, it was thought that within a few short years, the five genes behind obesity and diabetes, the dozen involved in schizophrenia, and the twenty affecting cognition would be located and big pharma would get to work developing drugs that mimicked—or blocked—the actions of these genes.
However, much to the disappointment of the medical establishment, it was soon learned that most outcomes—from height to heart disease—were influenced by thousands of locations across the human genome. Over time, however, researchers learned to summarize these miniscule effects into a single score, the polygenic index or PGI.
Today, we can swab a baby’s cheek and predict its adult height within an inch. Or take education: someone in the bottom 10 percent of the education PGI ranking has about an 8 percent likelihood of completing a four-year college degree; meanwhile, an individual in the top tenth has about a 70 percent chance of graduating with a bachelor’s degree. If you asked me to tell you whether your kid will get a Ph.D. based on their PGI, I would have a good chance of being wrong. But give me one hundred kids to test and rank order by education PGI, and the odds of predicting graduation outcomes for the top and bottom groups start tilting in my favor.
The age of genetic engineering may still be over the horizon, but the age of genomic prediction has dawned. This development has enormous implications for personalized medicine. For example, we can identify who is likely to develop early heart disease and administer statins from the time they turn 18. But the PGI will alter our social world even more radically than it will our medical treatment.
“We can swab a baby’s cheek and predict its adult height within an inch.”
PGIs are set to revolutionize domains ranging from education systems to insurance markets. For instance, insurance companies may adjust premiums based on your PGI; schools may request DNA samples as part of an application packet; dating apps may allow you to link to your 23andme account; and prospective parents may rank order the PGIs of in vitro embryos before deciding which to implant. It’s a brave new world of genetic prediction.
Indeed, in 2020, Aurora, the first PGI-selected baby, was born. While screening embryos for major chromosomal abnormalities (such as trisomy-21 a.k.a. Down’s Syndrome) has been fairly routine in most IVF clinics, what’s new here is that parents can choose which embryo to give a shot at life based on a rank ordering across dozens or even hundreds of traits—making tradeoffs between, say, the PGI for height and that for cognition or the PGI for depression versus the PGI for heart disease. Already, multiple fertility clinics are offering parents the chance to evaluate embryos on their genetic potential for various traits before deciding which one to implant.
Likewise, it will not be long before insurance companies (life, auto, long-term care) request genetic data to set premiums. Sperm and ova donor banks, dating sites, and even schools may get involved, utilizing the new science of genetic prediction. Moreover, since advantaged individuals will be able to leverage these new predictive technologies first, social inequalities will literally become baked into our DNA.
2. Genetic sorting is happening constantly and at all scales of society.
We may not be Pakistan or the UAE, where first-cousin marriage is the norm, but in the U.S. or Europe, we end up mating with people who are the genetic equivalent of our first cousins-once-removed. Our friends, meanwhile, are like our second cousins. If we look at particular genetic signatures—like that for education or height—we and our spouses are more like first cousins (for education) or even half-siblings (for height). When like mates with like, genetically speaking, the genetic inequality in the next generation increases, making it more and more intractable.
Moreover, people with differing genetic signatures—particularly with respect to educational and socioeconomic success but also height and BMI—even have differing numbers of children, which affects the average level of genetic risk in the population.
We can see this sorting at larger scales, too. For instance, those with disadvantageous genetic signatures for education are more likely to live in depressed, forgotten communities like the old coal mining towns of northern England. People who emigrate to new countries have more advantageous genes with respect to educational performance on average than those who stay behind. This is because people with a genetic propensity for education tend to abandon places without opportunity, leaving those left behind doubly disadvantaged—genetically and environmentally.
“People with a genetic propensity for education tend to abandon places without opportunity.”
Thus, we are not only increasingly polarized politically, we are literally genetically polarized, and social and genetic disparities are redoubled. Recognizing that we are literally different in our DNA may mean that we have to take much more drastic actions to remediate regional inequalities—like moving people around the country to mix it up rather than just providing tax breaks to distressed communities.
3. Even within our families, how we are treated is largely a function of our genes.
We typically think of socialization as a one-way street of parents actively or at least passively imposing their views, values, and skills onto their offspring, but it turns out that children “train” their parents as well. Indeed, most of the environmental influences that matter in terms of whom we become—like the proverbial 10,000 hours of training to master any skill—are, in fact, chosen by or evoked by our genes.
While this means that genes can’t often realize their effects without guiding us to the “right” environments, it also means that merely providing environmental opportunities to people doesn’t mean they will take advantage of them unless their genes want them to.
Our research found that this process starts at 12 months of age, when children who are a “high draw” in terms of their educational genetic potential evince more time to play and read from their parents than if they had a lower educational PGI. Research by a pair of economists shows that this dynamic flips by adolescence. Kids with lower genetic potential for education get the lion’s share of their parents’ attention and time investment. The straight-A student is left alone, while parents try to “save” the kid who is floundering. Parental behavior is an important social pathway by which the genes inside our bodies have their effects. That is, the effect of our genes doesn’t stop at our skin.
4. The metagenome (i.e., the genes of others) around you affects your behavior.
Even as the genes of a baby or toddler guide how parents nurture, the genes inside those parents also matter to the environment. Research has documented a phenomenon called “genetic nurture.” Namely, our parents’ genes affect us in two ways: They pass on 50 percent of them to us to work their magic inside our bodies and brains and in the environments we seek out, evince, or create. And our parents keep a copy behind of all their genes, which affects the way they parent us in important ways.
Part of what makes up critical social environments around us is the genes of the people around us. In this way, the social environment is, in part, genetics one-degree-removed. Here, too, the line between nature and nurture is fuzzy, and social and biological inequality is redoubled. But genetic nurture isn’t limited to our parents. For example: Your spouse’s genes affect your mood—i.e., likelihood of depression—almost a third as strongly as your own genes do.
“Part of what makes up critical social environments around us is the genes of the people around us.”
A final case in point: A few highly addictive genotypes can cause smoking rates to rise in an entire high school grade. The effects of our grade-mates’ genotypes may even be larger than that of our own genes (and those of our close friends), at least when it comes to smoking. Sociogenomics, then, has revealed that adolescent smoking is like a genetic wildfire that spreads and is difficult to contain.
5. How and how much genes matter depends on the environment.
In 1900, few people in America were overweight, let alone obese. Calories were scarcer, and we all generally lived more active lives. And back then, genes didn’t really predict our weight all that well. Today, of course, we are experiencing an obesity epidemic, and our genes predict our body mass index much better than ever before.
Meanwhile, in 1950, about half of Americans smoked, and genes didn’t really tell us much about who was or was not a smoker. After the 1964 Surgeon General’s report on the dangers of smoking, tobacco use steadily dropped, and who smokes has become much more a matter of genes. Only those genetically hard-wired to be addicted to nicotine become or stay smokers once the health information landscape changed.
In 1940, hardly any U.S. women completed college. Today, they outpace men in bachelor’s degrees. And, yes, differences in women’s genes now explain who has more or less education to a much greater extent than in prior epochs.
In all these examples, the environment shifted to provide more opportunity and information—that is, more informed choices—and genes, in turn, reared their head, engendering genetic inequality in the process. In short, the landscape of the environment is critical to if and how genes matter. This is the fundamental lesson of the sociogenomics revolution. This mutual dependence of genes and environment on each other for their effects augurs a world with genetically-tailored environments in the domains of health care, education, and so on.
To listen to the audio version read by author Dalton Conley, download the Next Big Idea App today:
