Nature + nurture = genetic nurture

February 14, 2018 - 06:20

Sequences of our parents’ genes that are not handed down to us can still shape our lives, according to new Icelandic research.

Can parents’ genes determine what sort of environment they create for their children? (Illustrative photo: KaliAntye / Shutterstock / NTB scanpix)

Nature or nurture, in other words, genes or environment?

Do you excel in school, are you plagued by anxiety or are you a substance abuser? Is this because of the genes you received from your parents, or the environment you grew up in?

The question of what factors form our personalities and fates have been debated for decades.

Complicating the nature-vs-nurture issues, the natural sciences and social sciences have often been institutionally and academically separated by a cloudy wall of misunderstandings and in some cases, by mutual disdain. And of course, the lines between nature and nurture cannot always be clearly drawn.

Icelandic researchers have now made the issue even more complicated and the demarcation line that much fuzzier.

They argue that parts of the environment impacting us can also have genetic components.

The genes you don’t have

The reasoning of Augustine Kong and her colleagues is based on the claim that much of the environment a person has is created by their parents.

Furthermore, parents’ genes impact the way they create this environment. 

In this way, parts of parental DNA can have an effect on how their children turn out, even when the kids do not inherit these traits genetically.

The researchers investigated this idea by looking at the education levels of over 20,000 Icelanders. A point of departure was something so often seen, that a person’s level of education tends to be affected by their genes and the environment in which they grew up.

Numerous gene sequences have been found by geneticists to be linked to how long people stay in school. One does not have to look too hard to see that children whose parents have college educations and academic careers tend to follow that route themselves more frequently than children whose parents took jobs that do not require college degrees.

The small island nation is a perfect place for studying such matters because the population is well documented and half of Icelanders have already been gene sequenced. This enables scientists to compare parents’ and their children’s’ genes with data about their educational levels.

Genetic environment

Kong and colleagues looked for various genes that impact the length of a person’s education. Moreover, they looked for a special combination – cases where one of the parents had such genes but their child or children had not inherited them.

They say that even then, the parent genes still had an impact on their children’s educational levels.

Each individual gene plays a minor role. But the combined effect of many genes controlling cognitive capabilities, for instance, could have a considerable impact on a child’s educational level even when these genes were not passed on to the child.

Kong and her fellow researchers think that these parent genes are shaping the environment their kids grow up in, and inherited family environments are influencing children’s educational success.

The researchers are calling the phenomenon genetic nurture.

30 percent

The impact of genetic nurture does not size up with the impact of actually inheriting the genes that help a kid do well in school, but they do contribute, conclude Kong and her colleagues. They estimate the effect of genetic nurture to be about 30 percent as strong as the effect of inheriting these genes.

They think it would be wise to try and determine exactly which genes are most important for the environment that parents create for their offspring. 

However, they point out that parents alone do not create the environment a child is raised in. There are all sorts of factors, notably siblings.

Interwoven mix

It will be intriguing to see how this notion of genetic nurture is received in scientific and research circles. Research in recent years – for instance epigenetics – has shown that genes and environment interact. Traumatic experiences in childhood can even change the way our genes work and can pass psychological and physical traits like anxiety or certain metabolisms on down the line one or two generations.

Researcher Piter Bijma at Wageningen University in the Netherlands is not surprised by the Icelandic results. According to the New York Times he thinks the findings also coincide with knowledge accrued about livestock, cows and calves. 

Psychologist K. Paige Harden and Economist Philipp Koellinger comment on the results in Science, the same journal in which the Icelandic study was published.

“Genetic nurture is a convincing example of how tightly tangled genetic and environmental mechanisms are,” write the researchers, who have not participated in the Icelandic study.

Harden and Koellinger think the new results highlight the challenges that dog researchers who try to understand human behaviour. 

“This illustrates how understanding heredity can give us tools for studying environment.”

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Read the Norwegian version of this article at forskning.no.

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Translated by
Glenn Ostling

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