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Lead book review

How Siddhartha Mukherjee gets it wrong on IQ, sexuality and epigenetics

We need a readable, authoritative popular guide to the latest developments in genetics. This, sadly, isn't it

28 May 2016

9:00 AM

28 May 2016

9:00 AM

The Gene: An Intimate History Siddhartha Mukherjee

The Bodley Head, pp.543, £25

Darwin came tantalisingly close to understanding them, 20th-century eugenicists obsessed over them, and with modern science, we are poised to control them as never before. Genes are a constant source of fascination, yet ignorance and misunderstanding plague almost every public discussion of their effects on our health and behaviour. How useful it would be, then, if there was a clear, accurate, and up-to-date pop science book on genetics, a book that recounted the history of genetic science and reflected on its implications for the future of medicine and society. This is the goal of the new book by oncologist-biologist Siddhartha Mukherjee.

It is a lofty goal, and Mukherjee attempts it with lofty language. Except where he throws in some jarring puns, his prose is impossibly grand, bordering on the grandiose. Occasional tinges of purple (‘ancient myth — of the child consuming its father, of Cronus overthrown by Zeus — is etched into the history of our genomes’) may set eyes rolling.

Thankfully, for most of the book, the flowery style doesn’t obscure Mukherjee’s compelling stories of scientific progress. Whether it’s Oswald Avery’s brilliantly straightforward 1944 pinpointing of DNA as the carrier of genetic information, Watson and Crick’s building and rebuilding of their man-sized model of its structure in the 1950s, or the quest to isolate the gene for Huntington’s disease in the 1980s and 1990s, what shines through is the sheer ingenuity of the scientists who have demystified the genome, searching for ‘laws’ that might undergird biology as they do physics.

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.

Stuart Ritchie is a postdoctoral research fellow in cognitive ageing at the University of Edinburgh.

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