Genetics and Violence


The publication in August in 'Science' magazine of the first strong evidence linking a specific gene to violent behaviour will come, in time, to be seen as a landmark in behavioural genetics. It should also be a wake-up call to critics of behavioural genetics: there is a desperate need to update and refresh arguments which are looking increasingly dogmatic and rusty.


The paper, by Caspi et al is significant not only for its findings but also for its methodology. Unlike previous studies, which have looked for direct links between genes and behaviour, Caspi et al looked at the interaction between their candidate gene, MAOA, and an 'environmental' variable, experience of abuse in childhood.The MAOA gene codes for monoamine oxidase, which eliminates excess neurotransmitters, such as norepinephrine, serotonin and dopamine, which are known to affect mood. Prior evidence, including the well-known study of a violent Dutch family with an MAOA mutation, and the established link between childhood abuse and later violent behaviour, made the search for interaction between these variables logical.


The study uses a group of New Zealand men and women that has been tracked since childhood. The researchers genotyped 442 young men for a MAOA variation which leads to low activity of the enzyme. They found that while there was no link between MAOA genotype and violence in the group as a whole, amongst men who had suffered abuse in childhood, those with low MAOA activity were nearly four times as likely to have been convicted of a violent crime by the age of 26.  Similar results were found with two other independent measures of antisocial behavior, making it unlikely that the results are artefactual.  85% of those with both risk factors, who were 12% of the total, developed some form of antisocial behaviour.


These findings, if replicated, are extremely significant. Although there is a long history of failure to replicate in behavioural genetics, and indeed in current attempts to identify genetic risk factors for common diseases, it would be unwise to assume that this will happen in this case. Unlike many behavioural genetics studies, the effect identified is large, probably largely due to the improved methodology: in previous studies the researchers attempted to identify genetic effects in the whole sample population, in which many subjects did not share the relevant environmental risk factor. Such studies generally find small, barely statistically significant effects which are not replicated. A similar problem is no doubt at the root of the failure of many current studies to find clear, replicable, disease susceptibility loci.


It seems likely, then, that MAOA variations have a strong effect on aggression in men who have suffered abuse. This will be hard to swallow for many liberals who still, with various degrees of sophistication, believe in a 'blank slate' model of human development. But swallow it we must, and find a way to digest it, too. Whilst many readers will not be too shocked by the idea that genes can affect behaviour, many liberals tend to cling to a comfortable scepticism about behavioural genetics. The most foolish aspect of this is the assumption that the long term and ongoing association of the field with eugenics and racism means that behavioural genetics is bad science. This is obviously wrong.  Liberal critics of behavioural genetics also tend to have vague ideas about the pitfalls of twin studies methodology and a feeling that IQ tests are racially biased.  But whilst some critiques of twin studies are still valid, on the whole our ideas about the scientific validity of behavioural genetics are out of date. Over the past 20 years, behavioural genetics has become much more sophisticated and has addressed many of the methodological criticisms; the Caspi et al study is the latest step in this process.  A significant body of evidence for genetic effects on behaviour now exists.  This study should serve as a catalyst for us to re-examine our critiques of behavioural genetics.


While it is impossible here to do justice to what a refreshed critical position on behavioural genetics would look like, the Caspi et al paper illustrates some key aspects of the problems raised by behavioural genetics.In my view, while the exploitation of behavioural genetics research by reactionary and racist political forces remains a threat, these are not its real driving forces.  Like the early 1990s Violence Initiative, this study was funded by medical research funding agencies, not crime prevention institutions.   Its most sinister aspect is its involvement in processes that are often mistaken for 'progress' by liberals: the control of social disorder through medicalisation. After all, what could be more benign and sensible than to prevent violence and disorder by 'helping' those children unlucky enough to have both suffered abuse and to carry a low activity MAOA allele, first by counselling and later, no doubt, by pharmaceutical intervention?   There can be no doubt that this will be irresistible to both liberal and conservative politicians.


In his 'The History of Sexuality', the French philosopher and sociologist Michel Foucault describes the emergence in the 18th century of a new form of power, 'bio-power'. Bio-power controls society through two intersecting approaches: the discipline and normalisation of individual bodies and the regulation of the population at large.  Its purpose is to control disorder and maximise the productive forces of the population for capital accumulation. Bio-power works through medicine, hygiene, manners and training on the one hand, and through the sciences of epidemiology, demography, sociology, and public health.  At the intersection of the population and individual arms of biopower lies eugenics.  Bio-power is not repressive: on the contrary, it seems benign, rational, progressive and sensible as it manages and marshals the forces of life.  By 'measuring, appraising and hierarchising, it effects distributions around the norm'. 


Behavioural genetics, with its emblem of the normal or Bell Curve, exemplifies bio-power and the work of Caspi et al, is a beautiful example of how it works.  The individualising power of genetics is currently driving a critical change in public health philosophy, away from the one-size-fits-all approach towards an even greater focus on identifying 'high-risk groups'.  Again, this seems benign and rational, a win-win situation for individuals and the state: why waste resources on those who are at low risk and fail to make the crucial preventive intervention on those who are high risk?  This approach, which encompasses both disease susceptibility and pharmacogenetics has been described as rational medicine, and is widely predicted to revolutionise the paradigm and structures of healthcare delivery. 


Yet, ironically, as a little reflection on Caspi et al will show, such a strategy risks disastrously backfiring when applied in the area of crime prevention. Even the most kind-hearted attempt to identify and 'help' those abused children with low activity MAOA alleles will almost inevitably do damage to their own self-identity and lead to their stigmatisation by others.  To label and medicalise these children can only give them the message that there is something deeply and intrinsically wrong and bad about them, and that everyone else thinks that they are the problem.  This is precisely the message they will have received from their abusers.   Such medical interventions are more likely to precipitate the kind of anti-social behaviour the doctors are seeking to prevent than almost anything else I can think of.  In turn, this will lead to a spiral of further interventions.  Any fool can see this. Any fool, that is, except a well-meaning scientist.  For Caspi et al are not reactionaries. Rather, this example illustrates beautifully the answer to the perennial question of why scientists lend themselves so willingly and easily to the purposes of capitalism. It is that combination of naivety and arrogance in which we train our scientists that allows them to overlook the obvious while believing they are doing unchallengeable good for the world.  Thus do the forces of bio-power and technocracy roll on.


For me, the most frightening aspect of behavioural genetics, is the far greater penetration that it gives to the powers of discipline, its ability to identify the problematic or dangerous individual and its opening of new, and commercially profitable, possibilities of normalisation through biological interventions.  The problem with behavioural genetics is not that it is simply part of an old-fashioned right wing agenda. We need a more realistic critique that questions its role in medicalisation and other benign-seeming processes of social control. 


There will no doubt be other studies of this kind, which will find strong links between genes and behaviour.  The lesson we should draw from Caspi et al is that we must stop hoping that behavioural genetics will fail, or that we can discredit it by linking it to racism.  I hope we can take this opportunity to re-examine our arguments.  If we fail to do so, for fear of conceding ground to eugenicists, we are likely to find ourselves increasingly irrelevant in the debate over the social policy implications of genetics.




1. Caspi, A. et al 2002 Science No 297 ps 851-854.
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