It’s complicated

Children are born to grow – physically, mentally, and emotionally. Yet how that plays out differs greatly from one child to another. Mozart famously started composing at the age of five, and the Hungarian mathematician John Neumann was just six years old when he first exchanged jokes with his father in ancient Greek. For a typically developing child of that age, in contrast, it is considered an accomplishment to draw a convincing picture of a person on a piece of paper.

Children’s growth is a product of both their inherited DNA and their environments. DNA is the language in which our genomes are written, and those genomes are essentially a vast collection of instruction manuals. So far, however, we have come to understand only part of their content. For example, we know that our genes direct the production of proteins, telling our cells which molecules to produce to support the functioning of our bodies. We also know that our behaviours and psychology are influenced by our inherited DNA. But how and why we go from protein building to learning or running is still rather mysterious.

None of the differences between children are due to DNA alone. Instead, genetics operates within children’s environments, which have an important effect on the development of individual characteristics.

“None of the differences between children are due to DNA alone. Instead, genetics operates within children’s environments, which have an important effect on the development of individual characteristics.”

How do genes and environment interact?

First, genes and environments build on one another. Children who have inherited a genetic preference for reading from their parents are likely to grow up in homes filled with books, because of their parents’ own genetic preference for reading. This phenomenon is known as ‘gene-environment correlation’, meaning that people tend to gravitate toward environments that correspond to their genetic predispositions. Thus, genes are not randomly distributed across environments; instead, genetic profiles are grouped into the environments that best suit them.

Second, environments regulate the influence that genes have on development. For example, some children with a genetic preference for reading may grow up in homes that lack books. These children will still be likely to enjoy reading, once they are exposed to books in school and at the library, but they may become less avid readers than if books had been readily available to them at home. This type of interaction is different from gene-environment correlation, in that rather than simply building on one another, the genes and the environment regulate each other’s effects.

Gene-environment correlations pose an ethical challenge

Just as children who are genetically blessed and grow up in privileged environments tend to become successful adults, children who are genetically less fortunate and raised in less advantaged environments are likely to grow up to be less successful.

Gene-environment interactions, however, offer a beacon of hope, as changing the environment could have positive effects on development. As sociologist Dalton Conley observes, “A gene for aggression lands you in prison if you’re from the ghetto, but in the boardroom if you’re to the manor born.” In other words, an individual’s environment may alter the effect that inherited DNA has on developmental outcomes.

“If we change children’s environments in a way that complements their genetics, we may be able to boost their strengths and soften their weaknesses.”

This makes intuitive sense; a person of average height who lives among giants is likely to stand up straight and grow strong neck muscles, while that same person might develop a hunchback when rooming with the seven dwarfs.

And herein lies the hope: If we change children’s environments in a way that complements their genetics, we may be able to boost their strengths and soften their weaknesses. For example, we might be able to increase the effectiveness of education interventions, which typically work for some but not all children. If we knew which children would be unlikely to respond to a certain intervention, for genetic reasons, we might offer them a different one that would be a better fit.