Book Review: The Social Genome – The new science of nature and nurture

The Social Genome: The New Science of Nature and Nurture
By Professor Dalton Conley
Published by WW Norton and Co
ISBN-10: 1324092637, ISBN-13: 978-1324092636
Buy this book from Amazon UK

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While sociogenomics is itself a relatively new field, the idea that underpins it – nature versus nurture – is a longstanding question in genetics and sociology. Are we on a path predetermined by the genes we inherit or are we a product of the social environment with which we interact?

The Social Genome: The New Science of Nature and Nurture is the eighth book written by Princeton University sociologist Professor Dalton Conley. Here, Professor Conley writes about the field of sociogenomics, exploring how the combined effect of genomic variants and the social environment shapes the outcomes of different individuals.

Very few diseases or traits are monogenic – that is, attributable to a specific variant of one gene, regardless of the environment with which you interact. You probably already know some of the diseases that manifest in this way, such as the BRCA mutation in breast cancer, or the mutations that lead to sickle cell anaemia or cystic fibrosis. But most diseases or conditions don't have such a linear, single-gene cause-and-effect. Certainly, most traits – a tendency to take greater risks or to be gifted in mathematics, music, or sport, for example – are far from monogenic, and far from independent of the social environment. Conversely, Professor Conley and others argue that looking at sociology in isolation is not a good predictor of individual outcomes either.

In The Social Genome, Professor Conley discusses whether a polygenic index (PGI), considered together with the social environment, can better capture the predictability of polygenic traits and their associated outcomes.

A polygenic index is a value determined by the total weighting of thousands of individual markers in a genome that are found to be associated with a specific trait. It is only really in the past 15 years that PGIs have taken off in social and behavioural sciences, and during this time, the predictive power of PGIs for certain traits has increased.

As described in the book, PGIs may be used within population health to try to predict the likelihood of an individual developing certain conditions, such as ADHD or depressive disorder, or to predict general cognitive ability (see BioNews 1192, 1285 and 1316). If we look at this through the lens of sociogenomics, we can begin to understand – at least to some extent – how a PGI, combined with social environment, might relate to the life outcomes of an individual.

Speaking at the recent PET (Progress Educational Trust) Annual Conference, behavioural geneticist Dr Emma Meaburn unpacked the terminology, explaining that the term 'polygenic index' (or the plural 'indices') is used if care is being taken not to imply a value judgement (where none is intended). In other contexts – particularly in the context of predicting disease (see BioNews 1320) – such indices are often referred to as 'polygenic scores', or 'polygenic risk scores'. Dr Meaburn also went into some detail explaining how these scores/indices are developed, building upon an earlier comment piece that she had written for BioNews (see BioNews 1302).

PGIs may be informative at a population level, but they are not proven predictors of individual traits. Certainly, our understanding of genomics and epigenetics is not at a point where we could (either with or without taking environmental factors into account) confidently use PGIs to predict someone's future A-level grades, their 100 metre sprint time, or their personality.

I felt that The Social Genome overreached in its suggestion that PGIs might be used as predictors of traits and outcomes with a strong degree of certainty. Granted, Professor Conley acknowledges that PGIs are not equally reliable across demographic groups. Most of the genomic data that underpins PGIs comes from people with white European ancestry. Consequently, PGIs are less reliable in relation to people who have non-European ancestry, and their use may exacerbate current inequities (see BioNews 1231, 1232, 1293, 1297 and 1300).

Even so, for someone less familiar with the field of genetics, it would be reasonable to come away from this book thinking that widespread PGI prediction on an individual basis will be an inevitable outcome for all demographic groups in the future, when this is by no means certain. In the final chapters of his book, Professor Conley cautions against placing too much emphasis on the predictive power of PGIs, but his narrative elsewhere contradicts this.

Professor Conley's approach to PGIs also veers occasionally into a specific kind of framing. He begins his book with a very open statement about how he wanted to use PGT-P (preimplantation genetic testing involving polygenic scores) to 'create the world's first PGI-optimised baby' by screening embryos for ADHD, schizophrenia or other neuropsychiatric traits. While he did not go ahead with this, it set a tone of hoped-for optimisation that continued throughout the book, regardless of Professor Conley's cautions around ethical and policy implications (see BioNews 1130, 1137, 1232 and 1253). It is worth noting that whereas PGT-P is available in the USA, it is not permitted in the UK (see BioNews 1319, 1325a and 1325b).

The Social Genome describes many examples of research – much of it led by Professor Conley – into the combined effect of genes and society, and this makes for an interesting catalogue of case studies. I also thought that the analogy of genes and environment behaving as a Möbius strip, threaded through the book, was a useful way of showing how these factors might interact.

Having said that, I am not sure the book's conclusions concerning nature and nurture progress the conversation much further than 'some of Column A, some of Column B'. There will likely be much more discussion about PGIs as technology and as research progresses (as indeed we are seeing in relation to assisted conception), but for now this is a topic that should be approached with caution.

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Buy The Social Genome: The New Science of Nature and Nurture from Amazon UK.