The debate of nature versus nurture is never simple, and one reason is because nature influences nurture. A father’s genetically predisposed anxiety will affect the environment he creates for his daughter, even if he doesn’t pass down the trait itself to his happy-go-lucky child. Scientists are now quantifying these effects in humans, and showing how the genes your parents don’t pass on can still influence you.
The key to today’s research, published in the journal Science, is a dataset of information from 20,000 Icelanders that included people and their parents. It has not only genetic data, but information about educational attainment (as measured by how many years of schooling someone received). Half of our DNA comes from each parent, so having DNA for all three makes it possible to separate what is directly inherited from what isn’t. Combined, the variants that weren’t passed down had an effect about 30 percent as big as the genes that were when it comes to educational attainment.
Genetic nurture is, in many ways, a very intuitive concept. “Everybody can appreciate that nurture is important and different parents provide different types of nurture,” explains study author Augustine Kong, a genomics researcher at the University of Oxford. (The research for this study, however, was done while he was with the Icelandic company deCODE.) But of course, how a parent provides nurture is related to the parent’s behavior — and the parent’s behavior is affected by their genes.
Previous research, such as one Nature study from 2016, have pinpointed genes that are associated with higher educational attainment. Kong stresses that these types of results aren’t deterministic, but are small genetic effects that add up on the population level. “Genes for education” don’t exist. Instead, these gene variants create biological changes that also interact with environmental and psychological changes.
It’s rare to find such a complete genetic dataset, but this strength is also a limitation, according to Kathryn Paige Harden, a psychologist at the University of Texas at Austin, who was not involved in the study. “Iceland is a radically homogenous population that lives under the same type of sociocultural and political context,” she says, “and so the extent to which these results would look exactly the same in another country remains to be seen.”
That said, the homogeneity of Iceland suggests that the effect of genetic nurture may be even stronger in other countries. “There is inequality everywhere in the world, but Iceland is probably among the places that has the least,” Kong says, pointing to the country’s universal healthcare and free higher education. “Even in a situation like this, we still see the effects of genetic nurture,” he adds. “I would speculate that if we had the proper data to investigate this phenomenon in the United States or the UK, this effect would likely only be stronger.”
Today’s findings add nuance to other genetic studies, and the method could be helpful for scientists studying nature versus nurture, according to Harden. Right now, we use adoption studies to separate the two because adopted parents are not genetically related to their children. (This isn’t a perfect method, though, because parents aren’t randomly approved for adoption. “In this study, they’re basically dividing the parent into two parents, and one of them is genetically an adoptive parent because these are genes that your mom has that you don’t share,” says Harden. “It’s a new method around disentangling why parents and children are similar.”
Though today’s study focused on one person and their parents, of course parents are influenced by their parents, and the chain continues. Now, Kong is interested in the overlap in the different genetic components. For example, it could be that one variant has a strong direct effect on a trait, but a strong nurturing effect on another trait. In terms of future research, “the best analogy I can think of is physics,” says Kong. “If you discover a new force, it can have an impact on everything, and my belief is that genetic nurture will have basically an impact on nearly all problems related to genetics.”