The DNA revolution: debate over nature versus nurture rages on

The results of the experiment that separated triplets at birth has failed to put to rest what really influences us

(left to right) Edward Galland David Kellman, and Robert Shafran. Courtesy of NEON
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"It was the first day of school and people were coming up to me saying, 'Eddy how are you?' 'Eddy, hi' and I thought, 'my name's not Eddy. I don't know what you are talking about'." So starts the extraordinary story of three young men, Robert Shafran, Eddy Galland and David Kellman, identical triplets who were separated at birth in New York in 1961, and reunited at the age of 19. The story became a media sensation as the world marvelled at how very similar the brothers were; their celebrity even led to a cameo role in Madonna's 1985 film Desperately Seeking Susan

There was a darker narrative at play, however; the triplets were part of a secret study, by child psychologist Dr Peter Newbauer, designed to determine whether genetics or our environment, nature or nurture, have greater influence in shaping our lives. The now-defunct New York adoption agency Louise Wise Services placed the triplets with different adoptive parents chosen for their different socio-economic status and monitored closely. None knew of the others' existence in an experiment that Eddy Galland calls "inhumane", as he and Robert Shafran tell their story one more time in the documentary Three Identical Strangers, directed by Tim Wardle. 

Half a century after the brothers were cruelly separated, the nature versus nurture debate still rages, not least because of a new book, Blueprint: how DNA makes us who we are, by Robert Plomin. "I'm saying that if you had been adopted at birth, reared in a different family, gone to a different school, had different friends, a different job, you would essentially be the same person in terms of personality, cognitive abilities and mental health," he tells The National.

The DNA revolution

The quietly spoken professor of behavioural genetics at King's College London could be speaking about the plot of Three Identical Strangers, but he's actually explaining the wider significance of recent advances in genetic testing. Advances that he believes should forever tip the scales in favour of genetics over environmentalism: "We are beginning to be able to read our DNA blueprint and predict psychological problems and promise from birth – and that's a game changer."

Plomin makes a compelling case for what he excitedly calls the DNA revolution. In the past few years geneticists have been able to access huge data samples to build up an increasingly broad picture of how tiny variations in the three billion base pairs of DNA that comprise the human genome, can predict the differences between us. Blood samples can now be analysed not just to uncover single-gene defects but also to determine probable psychological and personality traits, cognitive abilities and general health.

Robert Plomin says nurture makes no difference. Courtesy Robert Plomin

These polygenic scores can determine with increasing accuracy the likelihood of heritable characteristics within the general population. This in turn raises much larger questions about how this information might be used by governments and whether it should be made freely available to individuals. Would you like to know whether you’re likely to suffer from dementia in old age, for example? As a parent, would you like to know whether your child is likely to be a high academic achiever?

While Plomin makes sure to underline the probabilistic nature of polygenic scores – heritability, he writes more than once, "describes not what is but what could be" – genetics is the perfect fodder not only for documentaries but for dystopian novels and the darkest science fiction. The very idea of our DNA marching relentlessly into successive generations makes genetics unpopular, terrifying even. What about social mobility, critics ask. Then, there's the shadow of eugenics, the social and political movement that aimed for genetic purification and found its most terrible agents in Nazi Germany. Throw in the complexity of the science and it's hardly surprising that we're resistant to giving genetics its due. 

Nurture over nature?

It’s a reluctance that frustrates Plomin who cites recent debates in the British press about the correlation between the number of books in the home and how well kids are able to read at school, as an example our determination to cling to nurture over nature. “There was a push to say, ‘well, why don’t we just drive a van up to the home and drop off a lot of books and then all kids will read better.’ Well, I ask you: which parents have more books in their home? Which kids like to be read to? It drives me nuts a little bit, but there is movement, people are beginning to say, ‘Well, think about genetics’.”

It’s not that Plomin dismisses the influence of environmental factors. He readily acknowledges that the environment has an important role to play. After all, he says, if 50 per cent of who we are is genetically determined that leaves the remaining 50 per cent open to environmental influence; it’s just that those important environmental influences are random and unknown. 

In Blueprint, Plomin exhaustively details his own studies of identical twins separated at birth among other research findings to prove that systematic environmental factors (aka nurture), such as your familial upbringing or schooling, don't make a difference to outcomes (except in extreme circumstances such as neglect or abuse). It's also an interpretation that explains why siblings in the same family can be so wildly different.  

But if genetics and environmental factors are equal rivals, what makes genetics the more useful tool, Plomin argues, is that DNA can be analysed from birth – not to mention that the human genome doesn't change over a lifetime. Importantly, in Blueprint, the psychologist goes one step further to argue that environmental factors are also genetically modified by what he calls the nature of nurture: "The way genes work is to make people use their environment in different ways; they create their environment, they modify … they select environments that are correlated with their genetic tendencies," he says. "Take musically gifted kids: it's not that they are born that way, it's not hard-wired; it's just that they are tuned in to those stations. They don't need the world's best teacher, they will bang on pots, they will listen to the radio, they will hang out with friends who foster their interest in music."

Schooling doesn't make a difference to children’s achievement

Blueprint advocates a new way of thinking about parenting, even if some will find Plomin's conclusions rather stark: " … children are not blobs of clay that can be moulded however they wish," he writes.

“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.”

Shocking and profound it may be but Plomin is hoping for a positive outcome for parents in the DNA revolution. Rather than them being locked in perpetual anxiety that every little thing they do (wrong) will negatively affect their offspring, he argues that they can relax and do what comes naturally. “In the tumult of daily life parents mostly respond to genetically driven differences in their children, he writes. “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.”


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What parents might find even harder to swallow – Plomin admits, somewhat ruefully, that his conclusions often makes parents angry – is that schooling does not make a difference to children’s achievement. By analysing the GCSE results of 16-year-olds in schools in the United Kingdom, he explodes the assumption that selective schools provide better teaching and this in turn leads to better results. Instead he argues that children are “unintentionally selected genetically” because the traits used to select students are “highly heritable”.

"When we control the factors that are used to select students the average difference in GCSE exams is negligible," he writes, "and overall GCSE variance explained by school type shrinks to less than 1 per cent."

The flip side of his research findings, Plomin tells me, is that parents can forget school league tables and parenting techniques, and focus instead on the quality of their relationship with their children: “It only seems to me to be common sense if you think about parenting as a relationship, a loving relationship and I think it will be a lot better for parents and kids if they start thinking of it in this way.” 

"We can try to force our dreams on them … that they become a world-class musician or a star athlete," he writes in Blueprint. "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."