Nick Spencer reviews Denis Alexander’s book which explores the relationship between genetic determinism, free will and moral responsibility.

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Do you know that there is a gene for enjoying the Theos website? It’s just between the gene for being intelligent, thoughtful, and slightly too clever, and the one for being moral, upright and gently herbivorous. You may have it. Theos’ bloggers usually do. The Theos Research Director is allegedly terminal.

The absurdity of such an idea has not prevented many a journalist (or at least sub–editor) penning an article entitled “Scientists discover gene for X” when X = binge–drinking, being a caring man, believing in God, happiness, exam success, ruthlessness, or impulsivity (all genuine examples) and much else besides. It seems that now we have decoded the human genome, we are indecently keen to say what it actually does.

Alas, what is does is considerably more complex than headline, article or even, sometimes, scientific paper often claim. Indeed, perhaps the only honest answer is we just don’t know, even though we do know much more than we did even a decade ago. The problem, as is so often the case, is that the more we know, the more we realise there is to know.

Denis Alexander, having been Chairman of the Molecular Immunology Programme and Head of the Laboratory of Lymphocyte Signalling and Development at The Babraham Institute, Cambridge, knows the field from the inside. Moreover, as founding Director of the Faraday Institute for Science and Religion in Cambridge, he not only knows the science but has a lively and informed understanding of its historical, cultural, philosophical, and theological context and implications. Genes, Determinism and God, based originally on his 2012 Gifford Lectures at the University of St Andrews, touches on all of the above. It is a thorough, measured, rewarding, but demanding read.

Alexander’s key point – one might say target – is not so much the crass media–genery quoted above (too big and too easy a target) but the misleading dichotomous language that underpins it; the way in which human life have long been understood as nature or nurture, innate or learned, genetic or environmental.

Sometimes, in more sophisticated renditions, the ‘or’ becomes an ‘and’, as the journalist or popular science writer explains that both factors come into play. This is certainly better but still fails to capture the fundamental point, which Alexander stresses repeatedly throughout the book, that “all animal phenotypes are 100 per cent genetic and 100 percent environmental.” You cannot separate the genetic impact on an individual organism from the environmental impact, any more than you can the ingredients and the heat that go into baking a cake. We are stuck in the realm of “infinite regress [where] everything affects everything else”.

Where, we might then ask, do all the confusing stories and popular misconceptions about the balance of nature and nurture come from? The answer is surprisingly straightforward. Geneticists commonly talk about, and journalists commonly report on, ‘heritability’. In popular parlance, this is a measure of what you or I have inherited from mum or dad, as opposed to say what we’ve taken from our schooling, friends or some other environmental factor. In geneticists’ usage, however, heritability is a “statistical construct referring to variation in a population, [rather than] the interplay between genes and environment in any particular individual.”

By a variety of clever and complex devices, biologists are able to tell the extent to which a trait within a population can, within a certain margin of statistical significance, be accounted for by genetic inheritance. Thus, the claim that “55 per cent of intelligence is heritable” is actually the claim that 55 per cent “of the phenotypic variance in intelligence in a given population is attributable to genetic variation” and not that “55 per cent of an individual person’s intelligence is due to their genetic endowment from their parents.” It’s easy to see how the details get lost in the reporting but losing them confuses rather than clarifies the truth.

Alexander advocates a more satisfying model for ‘how genes work’ which he calls DICI, standing for Developmental Integrated Complementary Interactionism, an acronym which (like the book) is precisely chosen, accurate but difficult and, at first glance, bewildering. The model slowly becomes clearer (although not simpler) as he walks us through the science of nematode worms, fruit flies, voles, and humans, to questions of intelligence, religiosity, sexuality, and law, and finally the metaphysical twin peaks of free will and the image of God.

The journey is a long one and the gradient is sometimes excessively steep. Moreover, the conclusion, such as it is, will disappoint anyone who has digested the popular media stories. Most traits show some sign of heritability, virtually none are determined. “Figuring out how ‘genetic’ traits are… is a lost cause. Everything is genetic to some extent and nothing is completely so.” In spite of the hype of the last twenty years, the genetic book of life doesn’t offer any shortcuts to the meaning of human existence. Rather, like most sacred texts, it demands careful, patient, sceptical exegesis, which is exactly what Denis Alexander had granted it.

Genes, Determinism and God (2017) by Denis Alexander, published by Cambridge University Press

A version of this review was published in The Tablet