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Evan Horowitz | Quick Study

Educated parents have educated kids. Genes aren't the reason

GLOBE STAFF PHOTO ILLUSTRATION; ADOBE STOck

Here’s a tip for kids who want to get the most out of their education: Make sure you choose parents who already did.

While the children of highly educated parents have about a 50-50 shot at making it through college, the odds are worse than 1 in 10 for kids whose fathers dropped out of high school.

What’s behind these gaps, though? Is it genetics, with educational prowess passed from parents to children along strands of DNA? Or could it be environmental, given that better-educated parents tend to earn more, have more-stable marriages, and can often provide children with a richer and more nourishing environment?

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It may sound like an old, hoary question — nature vs. nurture — but not in the era of advanced genetic research, when scientists parse the genome and track the potential impact of teeny differences.

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One irony of this innovative research is that the closer scientists get to understanding the impact of individual genes, the smaller that impact seems to be — at least when it comes to education.

Yes, genetics plays a role, but the effect is not nearly so influential as researchers used to think. Other factors dominate, including not just the familiar environmental ones (income, quality of schools, parents’ ability to open doors) but also an unsuspected force: genes that parents don’t pass down to their kids.

For decades, the only rigorous way to approach such questions was via twin studies, built around the idea that genetics couldn’t possibly play a role in the different life outcomes of identical twins — but that it might with fraternal twins. Comparing these two groups could thus yield insights into the relative power of genes.

Now, however, scientists can dig a lot deeper, comparing hundreds of thousands of genetic differences across an entire population. One such effort, published in July in the journal Nature Genetics, looked at large swaths of the genome and found 1,271 genetic differences that seem to improve educational outcomes, including the amount of time spent in school. (On average, each adds 1.7 weeks.)

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Yet the authors calculate that the cumulative impact of these 1,271 educationally significant genes explains only 11 percent to 13 percent of the actual, real-world variation in educational attainment. And while you might think further research could improve on this by identifying other important genetic variants, perhaps not.

A separate paper, also published this summer in Nature Genetics, introduced a new technique for reassessing the role of inheritance on a variety of traits, including height, obesity, and education. In virtually every case, genes were found to play a smaller role than previously estimated — and a vastly smaller role than twin studies would suggest.

By the authors’ analysis, genes account for about 17 percent of the differences in how high people climb up the educational ladder. The rest is largely environmental. But there’s a twist, because it turns out there may be an overlooked third category playing a role in all of this, having to do with the genes parents have but don’t actually pass along.

Consider two parents who happen to have a suite of genes that make them slightly more attentive to kids and more willing to sacrifice their own happiness. Doubtless their kids will benefit from these genes, possibly including a richer education.

But it makes no difference whether the kids themselves get these genes. So should we call this effect environmental, because inheritance isn’t playing a role? Or is it still genetic, even if it’s just in the parents’ genome?

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The researchers take a Solomonic tack, calling the effect “genetic nurture.” And though it isn’t as life-shaping as your actual genes, genetic nurture may account for another 5 or 6 percent of the difference in people’s educational attainment.

Add it up, though, and you still see that genes play a supporting role. Having the right genetic variations seems to keep kids in school a little longer — though only a little. Having parents with the right genes probably helps a little more.

The rest of it is environmental, like whether you get the right emotional support, the right financial assistance, or some other needed boost along the way. That still seems to explain about three-quarters of the real-world variation in educational attainment.

And that may count as good news from a policy perspective.

For traits like height or eye color, which are more strongly affected by genes, it’s harder to conceive of social programs that would actually make a difference, at least without wending into the dystopian: Draconian mating policies to increase the prevalence of blue eyes, or research into height-enhancing drugs.

But if the science is right, and kids’ ability to graduate from college isn’t strongly shaped by their genes, it means that tweaks to the environment — better schools, better anti-poverty programs — could potentially have a big effect.

Evan Horowitz digs through data to find information that illuminates the policy issues facing Massachusetts and the nation. He can be reached at evan.horowitz@globe.com. Follow him on Twitter @GlobeHorowitz.