Why DNA may matter more than parenting — and what that means for society

But still, genes are not destiny — this just means we should tweak our strategies for parenting

Published November 23, 2018 1:00PM (EST)

"Blueprint: How DNA Makes Us Who We Are" by Robert Plomin  (MIT Press/Getty/Firstsignal)
"Blueprint: How DNA Makes Us Who We Are" by Robert Plomin (MIT Press/Getty/Firstsignal)

Adapted from "Blueprint: How DNA Makes Us Who We Are" by Robert Plomin. Copyright 2018, The MIT Press.

Parents obviously matter tremendously in their children’s lives. They provide the essential physical and psychological ingredients for children’s development. But if genetics provides most of the systematic variance and environmental effects are unsystematic and unstable, this implies that parents don’t make much of a difference in their children’s outcomes beyond the genes they provide at conception. This even includes personality traits that seem especially susceptible to parental influence such as altruism, kindness and conscientiousness. The only exception from hundreds of traits that shows some evidence of shared environmental influence are religious and political beliefs. As a parent, you can make a difference to your child’s beliefs, but even here shared environmental influence accounts for only 20 per cent of the variance.

Furthermore, when differences in parenting correlate with differences in children’s outcomes, the correlation is mostly caused by genetics. These correlations are caused by the nature of nurture rather than nurture. That is, parenting correlates with children’s outcomes for three reasons considered earlier. One reason is that parents and their children are 50 per cent similar genetically. Put crudely, nice parents have nice children because they are all nice genetically. Another reason is that parenting is often a response to, rather than a cause of, children’s genetic propensities. It is awkward to be an affectionate parent to a child who is not a cuddler. Finally, children make their own environments, regardless of their parents. That is, they select, modify and create environments correlated with their genetic propensities. Children who want to do something like play sports or a musical instrument will badger their parents to make it happen.

In essence, the most important thing that parents give to their child is their genes. Many parents will find this hard to accept. As a parent, you feel deep down that you can make a difference in how your children develop. You can help children with their reading and arithmetic. You can help a shy child overcome shyness. Also it seems as if you must be able to make a difference because you are bombarded with child‑rearing books and the media telling you how to do it right and making you anxious about doing it wrong. (These books are, however, useful in providing parenting tips, for example, about how to get children to go to sleep, how to feed fussy children and how to handle issues of discipline.)

But when these best‑selling parenting books promise to deliver developmental outcomes, they are peddling snake oil. Where is the evidence beyond anecdotes that children’s success depends on parents being strict and demanding "tigers" or giving their children grit? There is no evidence that these parenting practices make a difference in children’s development, after controlling for genetics.

This conclusion is also difficult for many of us to accept in relation to our own parents. As you think about your childhood, your parents no doubt loom large, seeming to be the most significant influence in your life. For this reason, it is easy to attribute how we turned out, in good ways and bad, to our parents. If we are happy and confident, we might credit this to our parents’ love and support. Or if we are psychologically damaged, we might blame this on inadequate parenting. However, the implications of genetic research are just as applicable here. These differences in parenting are not correlated with differences in children’s outcomes once you control for genetics. Your parents’ systematic influence on who you are lies with the genes they gave you.

If you are still finding it difficult to accept that parenting is less influential than you thought, it might be useful to review two general caveats about genetics. The first caveat is that genetic research describes what is, not what could be. Parents can make a difference to their child but, on average in the population, parenting differences don’t make a difference in children’s outcomes beyond the genes they share. Parents differ in how much they guide their children in all aspects of development. They differ in how much they push their children’s cognitive development, for example in language and reading. Parents also differ in how much they help or hinder their children’s self‑esteem, self‑confidence, determination, as well as more traditional aspects of personality such as emotionality and sociability. But in the population, these parenting differences don’t make much of a difference in their children’s outcomes once genetics is taken into account. Over half of children’s psychological differences are caused by inherited DNA differences between them. The rest of the differences are largely due to chance experiences. These environmental factors are beyond our control as parents, and yet we don’t even know what these factors are.

The second caveat is that genetic research describes the normal range of variation, genetically and environmentally. Its results do not apply outside this normal range. Severe genetic problems such as single‑gene or chromosomal problems or severe environmental problems such as neglect or abuse can have devastating effects on children’s cognitive and emotional development. But these devastating genetic and environmental events are, fortunately, rare and do not account for much variance in the population.

Again, parents and parenting matter tremendously, even though differences in parenting do not make a difference in children’s psychological development. Parents are the most important relationship in children’s lives. Still, it is important that parents get the message that children are not blobs of clay that can be moulded however they wish. Parents are not carpenters building a child by following a blueprint. They are not even much of a gardener, if that means nurturing and pruning a plant to achieve a certain result. The shocking and profound revelation for parenting from these genetic findings is that parents have little systematic effect on their children’s outcomes, beyond the blueprint that their genes provide.

It is also important for parents to know that, beyond genetics, most of what happens to children involves random experiences over which parents have no control. The good news is that these don’t make much of a difference in the long run. The impact of these experiences is not stable across time. Some children bounce back sooner, some later, after difficult experiences such as parental divorce, moving house and losing friends. They bounce back to their genetic trajectory.

In the tumult of daily life parents mostly respond to genetically driven differences in their children. This is the source of most correlations between parenting and children’s outcomes. We read to children who like us to read to them. If they want to learn to play a musical instrument or play a particular sport, we foster their appetites and aptitudes. We can try to force our dreams on them, for example, that they become a world‑class musician or a star athlete. But we are unlikely to be successful unless we go with the genetic grain. If we go against the grain, we run the risk of damaging our relationship with our children.

Genetics provides an opportunity for thinking about parenting in a different way. Instead of trying to mold children in our image, we can help them find out what they like to do and what they do well. In other words, we can help them become who they are. Remember that your children are 50 per cent similar to you. In general, genetic similarity makes the parent–child relationship go smoothly. If your child is highly active, chances are that you are too, which makes the child’s hyperactivity more acceptable. Even if you both have short fuses, you can at least understand it better if you recognize your genetic propensities and work harder to defuse situations that can trigger anger. It is also useful to keep in mind that our children are 50 per cent different from us and that siblings are 50 per cent different from each other. Each child is their own person genetically. We need to recognize and respect their genetic differences.

Most importantly, parents are neither carpenters nor gardeners. Parenting is not a means to an end. It is a relationship, one of the longest lasting in our lives. Just as with our partner and friends, our relationship with our children should be based on being with them, not trying to change them.

I hope this is a liberating message, one that should relieve parents of the anxiety and guilt piled on them by parent‑blaming theories of socialization and how‑to parenting books. These theories and books can scare us into thinking that one wrong move can ruin a child forever. I hope it frees parents from the illusion that a child’s future success depends on how hard they push them.

Instead, parents should relax and enjoy their relationship with their children without feeling a need to mold them. Part of this enjoyment is in watching your children become who they are.

Schools matter, but they don’ t make a difference

The same principles apply to education. Schools matter in that they teach basic skills such as literacy and numeracy and they dispense fundamental information about history, science, math, and culture. That is why basic education is compulsory in most countries around the world. Schools also matter because children spend half of their childhood in school.

But our focus is on individual differences. Children differ a lot in how well they do at school. How much do differences in children’s school achievement depend on which school they go to? The answer is not much. This conclusion follows from direct analyses of the effect of schools on differences in students’ achievement and is especially true when we control for genetic effects.

In the UK "league tables" rank schools by their average differences in tested achievement. In addition, rigorous government inspections of schools rank them by their quality of teaching and the support they give their pupils. Schools differ on average for both indices, but the question here is how much variance in student achievement is explained by schooling. These indices lead parents to worry about sending their children to the best schools, based on the assumption that schools make a big difference in how much children achieve.

In fact, differences in schools do not make much of a difference in children’s achievement. Most striking are results using the intensive and expensive periodic ratings of school quality, including teacher quality and the atmosphere of the school, based on visits to each school every three years or so by a team of assessors from the UK Office for Standards in Education (Ofsted). We correlated these Ofsted ratings of children’s secondary schools with the children’s achievement assessed on the General Certification of Secondary Education (GCSE) tests administered to UK students in state‑supported schools at the age of sixteen. The Ofsted ratings of school quality explained less than 2 per cent of the variance in GCSE scores after correcting for students’ achievement in primary school. That is, children’s GCSE scores scarcely differ as a function of their schools’ Ofsted rating of quality. This does not mean that the quality of teaching and support offered by schools is unimportant. It matters a lot for the quality of life of students, but it doesn’t make a difference in their educational achievement.

The conclusion that schools do not make much difference in children’s achievement seems surprising, given the media attention on average differences between schools in student performance. This reflects the confusion between average differences and individual differences. Average differences between schools in the league tables mask a wide range of individual differences within schools, meaning that there is considerable overlap in the range of performance between children in the best and worst schools. In other words, some children in the worst schools outperform most children in the best schools. The biggest average difference in achievement is between selective and non‑selective schools.

Inherited DNA differences account for more than half of the differences between children in their school achievement. Genetics is by far the major source of individual differences in school achievement, even though genetics is rarely mentioned in relation to education.

Environmental factors account for the rest of the variance in school achievement, but most of these environmental differences are not the result of systematic and stable effects of schooling. Environmental influence shared by children attending the same schools as well as growing up in the same family accounts for only 20 per cent of the variance of achievement in the school years and less than 10 per cent of academic performance at university.

The other crucial finding about the environment is the nature of nurture. What look like environmental effects are reflections of genetic differences. In relation to education, what looks like environmental effects of schools on children’s achievement are actually genetic effects. Examples include the correlation between student achievement and types of school and the correlation between parent and offspring educational achievement. Both correlations are usually interpreted as being caused environmentally but both are substantially mediated by genetics.

No specific policy implications necessarily follow from finding that inherited DNA differences are by far the most important source of individual differences in school achievement and that schools make so little difference. Similar to the message for parents, genetic research suggests that teachers are not carpenters or gardeners in the sense of changing children’s school performance. Rather than frenetic teaching in an attempt to make pupils pass the tests that will improve their standing in league tables, schools should be supportive places for children to spend more than a decade of their lives, places where they can learn basic skills like literacy and numeracy but also learn to enjoy learning. To paraphrase John Dewey, the major American educational reformer of twentieth century, education is not just preparation for life – education is a big chunk of life itself.

Life experiences matter, but they don’ t make a difference

Genetic research has far‑reaching implications not just for how we think about child‑rearing and schools but how we think about our own adult lives. Genetics is the major systematic influence in our lives, increasingly so as we get older. Therefore, genetics is a big part of understanding who we are. Our experiences matter a lot – our relationships with partners, children and friends, our occupations and interests. These experiences make life worth living and give it meaning. Relationships can also change our behavior, such as helping us to stop smoking or lose weight. They can affect our lifestyle by encouraging us to exercise, play sports and go to cultural events. But they don’t change who we are psychologically – our personality, our mental health and our cognitive abilities. Life experiences matter and can affect us profoundly, but they don’t make a difference in terms of who we are.

This conclusion follows from the same suite of genetic findings that we have applied to parenting and schooling: significant and substantial genetic influence, the nature of nurture and the importance of non‑shared environment.

Individual differences in stressful life events were among the first environmental measures for which genetic influence was found. Most research on life events used self‑report measures of stressful events and their effects. However, we saw that even objectively measured events such as divorce show genetic influence. Parental divorce is the best predictor of children’s divorce, but this correlation, easily interpreted as environmental, is entirely due to genetics. Quality of social support is another major aspect of life experiences that has been assumed to be a source of environmental influence but is in fact substantially caused by genetic differences.

Finding genetic influence on individual differences in ‘environmental’ measures led to research that showed that genetics accounts for about half of the correlations between life experiences and psychological traits, such as the correlation between perceptions of life events and depression. This is another example of the nature of nurture.

The point is that life experiences are not just events that happen haplessly to us as passive bystanders. With all our genetically rich psychological differences, we differ in our propensities to experience life events and social support. The nature of nurture suggests a new model of experience in which we actively perceive, interpret, select, modify and create experiences correlated with our genetic propensities.

The importance of non‑shared environment has major implications as well for understanding why life experiences don’t make a difference psychologically. The heritability of life experiences is about 25 per cent, which means that most of the individual differences in life experiences are environmental in origin. But these environmental influences are not shared by our siblings, even if our sibling is our identical twin. Our parents cannot take much credit or blame for how we turned out, other than via the genes they gave us. No one can take credit or blame because these non‑shared environmental influences are unsystematic and unstable. Beyond the systematic and stable force of genetics, good and bad things just happen. As mentioned earlier in relation to parenting, the good news is that these random experiences don’t matter much in the long run because their impact is not long‑lasting. We eventually rebound to our genetic trajectory. To the extent that our experiences appear shared, systematic and stable, they reflect our genetic propensities. These correlations are caused genetically, not environmentally.

In summary, parents matter, schools matter and life experiences matter, but they don’t make a difference in shaping who we are. DNA is the only thing that makes a substantial systematic difference, accounting for 50 per cent of the variance in psychological traits. The rest comes down to chance environmental experiences that do not have long‑term effects.

Many psychologists will be aghast at this bold conclusion. Karl Popper said that the first commandment of science is that theories are not merely testable but falsifiable. Falsifying this conclusion is straightforward: Demonstrate that ‘environmental’ factors such as parenting, schooling and life experiences make a difference environmentally after controlling for genetic influence. Anecdotes are not enough, and it’s not enough to show a statistically significant effect – the issue is whether these things explain more than 1 or 2 per cent of the variance. I am not worried about the conclusion being falsified, because there is a century of research behind it.

One general message that should emerge from these discoveries is tolerance for others – and for ourselves. Rather than blaming other people and ourselves for being depressed, slow to learn or overweight, we should recognize and respect the huge impact of genetics on individual differences. Genetics, not lack of willpower, makes some people more prone to problems such as depression, learning disabilities and obesity. Genetics also makes it harder for some people to mitigate their problems. Success and failure – and credit and blame – in overcoming problems should be calibrated relative to genetic strengths and weaknesses.

Going even further out on this limb, I’d argue that understanding the importance of genetics and the random nature of environmental influences could lead to greater acceptance and even enjoyment of who we are genetically. Rather than striving for an ideal self that sits on an impossibly tall pedestal, it might be worth trying to look for your genetic self and to feel comfortable in your own skin. Moreover, as we have seen, with age, as genetic influence increases, the more we become who we are.

By pointing out that most of the systematic variance in life is caused by inherited DNA differences I do not mean to imply that people should not try to work on any of their shortcomings or not try to improve certain aspects of themselves. Heritability describes what is but does not predict what could be, as I have emphasized several times. High heritability of weight does not mean there is nothing you can do about your weight. Nor does heritability mean that we must succumb to our genetic propensities to depression, learning disabilities or alcohol abuse. Genes are not destiny. You can change. But heritability means that some people are more vulnerable to these problems and also find it more difficult to overcome them.

"If at first you don’t succeed, try, try again" (Thomas Palmer); "Be all that you can be" (US Army); "Anyone can grow up to be President" (Americans) – throughout our lives we are bombarded with inspirational aphorisms like these, from childhood songs like the itsy‑bitsy spider climbing up the water spout and stories like "The Little Engine that Could" to adult fables like Robert the Bruce watching a spider repeatedly trying to build a web, as well as many autobiographies, novels and films about overcoming the odds. The barrage also comes from pop‑psychology books whose message is that all you need to succeed is some panacea, such as the power of positive thinking or a growth mindset or grit or 10,000 hours of practice.

Anyone who is influenced by these maxims should understand that, to the contrary, genetics is the main systematic force in life. Again, this is not to say that genes are destiny. It just seems more sensible, when possible, to go with the genetic flow rather than trying to swim upstream. As W. C. Fields said, "If at first you don’t succeed, try, try again. Then quit. There’s no use being a damn fool about it."

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Adapted from "Blueprint: How DNA Makes Us Who We Are" by Robert Plomin. Copyright 2018, The MIT Press.

By Robert Plomin

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