Stuart Ritchie writes: But although Mukherjee is awed by the intelligence of geneticists, he doesn’t think much of scientific attempts to measure intelligence. Indeed, in one chapter he launches an all-out attack on IQ tests. Why study the genetics of general intelligence, Mukherjee asks, when new evidence from the psychologist Howard Gardner shows that there are actually multiple intelligences? This will come as a surprise to Gardner, who has never provided any data for his now-debunked ‘multiple intelligences’ theory. In fact, general intelligence is probably the most well-replicated phenomenon in all of psychological science. But how would Mukherjee know this? His reading of the research on intelligence is cursory and out of date; he fails to cite a single scientific paper on the genetics of intelligence more recent than 2003, with most sources coming from the 1970s or earlier.
This lapse in scholarship is made all the more frustrating in the next two chapters, where Mukherjee discusses gender, sexuality and personality, happily concluding that they are all strongly genetically influenced. Perhaps he thinks IQ is one controversy too far. But a glance at the scientific literature shows that the research on the genetics of intelligence is vastly more developed than on, say, sexuality. No attempt is made to cover intriguing (and solid) findings such as the increasing genetic effect on IQ with age, or the first glimmers in large gene-hunting studies of DNA variants linked to more efficient brains.
Another underdeveloped topic examined in The Gene is ‘epigenetics’, the notion that the environment leaves marks on the genome that switch genes on and off, with concomitant health effects. Might these marks be passed on to our children, and even grandchildren? Mukherjee’s recent New Yorker essay on this topic angered scientists because it signally failed to acknowledge other genetic ‘switches’ that are far better known. That essay’s magpie-like focus on the shiny new ideas of epigenetics is not found in the book, but Mukherjee still leans too heavily on studies of the effects of the Dutch famine of 1944 — which do not rule out non-epigenetic explanations — and dismissively relegates alternative views (which are far more in line with the limited evidence on epigenetics) to a footnote.
What of the future? In The Gene’s final section, we get a little on embryo selection, a little on gene editing and a little on stem cells, all of which may soon be used to ‘engineer’ healthier, smarter or otherwise altered humans. The book’s coverage of these techniques — on which the importance of a full, frank debate cannot be overstated — is accompanied by a vague ‘manifesto’ on some of their pitfalls and caveats, but the whole treatment feels rushed, as if Mukherjee didn’t wish to scare the horses by getting too far into the ‘newgenic’ implications.
This disappointing failure to grasp the genetic nettle can be illustrated by a quotation from Mukherjee’s section on IQ tests. ‘Is g [general intelligence] heritable? In a certain sense, yes.’ Alas, the ‘certain sense’ here really means ‘after much qualification’; in fact, after so much qualification that you’ll go away thinking the answer is actually ‘no’, and not worrying too much about it. So, in the same spirit: is The Gene worth reading? In a certain sense, yes.
