children who have genes that correlate to more success in school evoke more intellectual engagement from their parents than kids in the same family who don’t share these genes. This feedback loop starts as early as 18 months old, long before any formal assessment of academic ability. Babies with a PGI that is associated with greater educational attainment already receive more reading and playtime from parents than their siblings without that same genotype do. And that additional attention, in turn, helps those kids to realize the full potential of those genes, that is, to do well in school. In other words, parents don’t just parent their children — children parent their parents, subtly guided by their genes.
Even the historical era and social conditions into which a child is born — their environment writ large — can affect how their genes do or do not find expression.
Take the PGI associated with body mass. A hundred years ago, when calories were more scarce and physical labor was more common, genes didn’t play much of a role in predicting who would become thin or heavy. The overwhelming majority of people were thin, and that was that. Fast-forward to today when both kale salads and venti Frappuccinos are available in abundance, and suddenly we see much wider variation in body mass index — and research I led suggests that PGI plays a bigger role in determining B.M.I. than it had in the past.
That’s the central insight of sociogenomics: Genes alone aren’t enough to determine these outcomes and neither is environment, but it’s not just because nature and nurture both shape the individual. It’s because they both shape each other, with nature influencing the way we experience nurture and nurture influencing the way our nature expresses itself.
Smoking offers another example. In 1950, almost half of Americans smoked. It was such a common activity that genetic variation didn’t play much of a role in determining who did or didn’t take it up. That changed after the 1964 surgeon general’s report on the dangers of smoking (and subsequent interventions). Today just over a tenth of Americans smoke. Doing so reflects a much more particular act. In this environment, research I was involved with has shown, smokers have a much higher average PGI for smoking than the rest of the population does.
In both of these examples, the more opportunities and information the environment provides — the more varied environments become — the bigger the role that genetic variation plays in sorting us into different categories.
This sorting is happening spatially, too. Many different factors come to bear on people’s decisions to leave the places they live in search of opportunity. Education turns out to be one of them: Studies, including ones I’ve worked on, show that those who have more schooling are more likely to make that choice. Because we know that there’s a correlation, however loose, between education PGIs and how far people go in their schooling, migration of diplomas also, to some extent, means a migration of genes, as studies have shown. A result is that societies are becoming not just economically polarized; they may be becoming biologically polarized, too. If so, this will have serious implications for economic opportunity that public policy will have to reckon with.
Genetic sorting is happening even in our most intimate environments. Looking across the whole genome, people in the United States tend to marry people with similar genetic profiles. Very similar: Spouses are on average the genetic equivalents of their first cousins once removed. Another research project I was involved with showed that for the education PGI, spouses look more like first cousins. For the height PGI, it’s more like half-siblings.
— Read on archive.ph/twY6f
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