GENE PULL

When Robert Plomin made himself the first guinea pig for his “polygenic” mapping – scoping people’s genetic make-up to see how prone they are to various traits – he learnt something no one wants to hear: he was in the 95th percentile for obesity.

Though these were extremely dismaying odds, they were no surprise to the self-described “portly” King’s College London psychologist and behavioural geneticist; he was excited. In keeping with his thesis that genes are exponentially more important than environmental factors in determining what we are like as individuals, he saw his fat-destiny diagnosis as a potentially powerful tool. If parents know early on that, for a particular child, keeping weight off or concentrating on tasks or battling serious anxiety are going to be lifelong challenges, they and the child will be better prepared to fend off those potential problems.

Plomin says it’s just as useful to be forewarned about any positive traits or distinctive tendencies our genes have dealt us, so we don’t waste time and effort working against them.

What did initially dismay him about his polygenic project was that it appeared to overturn a fundamental tenet of the behavioural psychology he had spent his career studying and teaching. His research had found that, although nurture can modify nature, the power balance is strongly tilted toward nature as the prime determinant of who we are.

Naturally, given that so much is invested in the power of nurture, not everyone is buying Plomin’s headline advice from his latest book Blueprint: How DNA makes us who we are – that parenting isn’t nearly as influential as we’d like to think, and that it can’t override genetics.

Research into twins supplies a persuasive thread of the findings Plomin draws on. Separated twins raised in different families will show the same basic traits in relation to body-mass index, irrespective of those of their adoptive families. In other words,