IQ is genetically inherited. It’s best for children—and parents—that we admit it
by Philip Ball / March 16, 2016 / Leave a comment
A display representing a DNA sequence at the Science Museum, London. ©John Goode
Read more by Philip Ball: Will gravitational waves help us discover cosmic strings?
Psychologist Oliver James’s claim, in his new book Not In Your Genes, that personality traits such as intelligence are not genetically inherited has been widely and rightly denounced by scientists. It is flatly contradicted by an abundance of hard data, which shows for example that IQ may have as much as 80% of an inherited component. To suggest otherwise amounts to scientific denialism.
James has said the turning point came when he read a comment in 2014 from Robert Plomin, a behavioural geneticist at King’s College London and a leading expert in the genetic aspects of intelligence, saying that after searching for 15 years for genes relating to inheritance, “I don’t have any.” Many candidate genes have been mooted, only for the evidence of an effect to evaporate when larger samples are analysed. Later in 2014 Plomin was part of an international team that identified three genes with an apparently robust link to IQ—but collectively they seemed able to account for just 1.8 IQ points.
Why, when heritability studies show so clearly that IQ (whatever that measures) must be partly “in our genes,” it is so hard to figure out which genes is still a mystery. No one expects a trait as complex as intelligence to be governed by just one or a few genes; some estimates put the figure as something more like hundreds, perhaps even thousands. On the one hand this makes it less surprising that pinning effects to specific genes is so hard. On the other hand it raises the question of exactly what it could mean to say that these genes are “for” intelligence. Most if not all would almost certainly have biochemical roles some distance removed from anything easily connected to brainpower, and which probably serve other essential functions too (which is why talk of editing the human genome to breed super-intelligence seems fanciful).
This difficulty of linking the direct roles of genes to the phenotype (traits) of an organism is a general challenge for modern genetics, affecting in particular efforts to identify the genetic origins of inherited diseases. Some think it will require new ideas about…
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