Criminal Genes?

Can genes predispose a person to crime? Some American lawyers are now using such a “genetic defense” as mitigation for convicted murderers. Are there genes for alcoholism? Or genes that make you gay, religious, prone to divorce, or even genes that determine how you vote? If you believe the claims of some of the scientists who call themselves “behavior geneticists”, many aspects of human behavior are in some way laid down by our genes.

Claims of this type have a long, discredited history, stretching back through the eugenics movement of the early 20th century to its acknowledged ‘father,’ Francis Galton, in Victorian England. But whatever the eugenics movement’s extravagant claims and social crimes, including the forced sterilization of thousands (mainly women) in Europe and the US, today it is supposed to be different. Today, the claims are supposedly backed by advances in real molecular science, in genetics.

Of course, many social problems run in families; our societies are not egalitarian; people living in poverty tend to rear children who live in poverty. This doesn’t, however, make poverty genetic. Similarly the children of rich parents may inherit wealth, but this is social, not genetic inheritance.

Sorting out the influence of genes and environment during the long, complex processes of human development is difficult – indeed, it is never possible to say of any individual, that x% of some aspect of their character is genetic, y % environmental. The two are indissolubly associated over the many years during which we construct ourselves out of the raw material of genes and environment. What geneticists do try to do is to find a measure of how much of the variation in some trait within a population may be attributed to genes, and whether any specific genes play a part in generating that trait.

While it is possible to do this for diseases where the diagnosis is relatively unambiguous and there is only a single abnormal gene associated with the condition (Huntington’s disease is a good example), this is a far cry from saying that a specific gene causes you to be criminal or alcoholic. Genes certainly help shape our behavior, but that behavior is profoundly mediated by the processes of development, culture, social environment, and even technology. It is impossible to speak of genes that ‘determine’ any complex aspect of human thought or action.

Take ‘aggression’. We use the word to mean many different types of behaviour. We speak of aggressive businessmen, or aggressive surgery, in positive terms. But we also speak of men’s aggressive behaviour to their partners or children, aggressive confrontations among football fans, or of police against protestors. We also speak of waging aggressive war. Are all these manifestations of the same ‘condition?’

Complicating matters, the same act involving the same genes, muscles and so forth, can sometimes be seen as criminally aggressive and sometimes as doing your duty. Take the case of the British soldier Lee Clegg who, while on duty in Northern Ireland, shot and killed a teenage joyrider whose car failed to stop at a security check. Clegg was tried, convicted, and imprisoned for murder but had his conviction quashed and was reinstated – and then promoted – in the army. So, did he have genes for criminal aggression, or is he a good soldier? If this ‘aggression phenotype’ is so poorly defined how can we hope to study its genetics?

Sadly, this hasn’t stopped people from trying. This is illustrated by a research paper‚ published in the journal Science in 1993 by a team led by Han Brunner describing a Dutch family some of whose men were reported as being abnormally violent. In particular, eight men “living in different parts of the country at different times across three generations showed an ‘abnormal behavioural phenotype.’” The types of behavior included “aggressive outbursts, arson, attempted rape and exhibitionism.” Can such widely differing types of behavior honestly be subsumed under the single heading of aggression?

Such an assertion, if made in the context of a study of non-human animal behaviour, would not be likely to pass scientific muster. Yet Brunner's paper was published in one of the world’s most prestigious journals to considerable publicity.

Much attention was devoted to its report that each of these ‘violent’ individuals also carried a mutation in the gene coding for the enzyme monoamine oxidase‚ (MAOA). Could this mutation be the ‘cause’ of the reported violence?

Brunner subsequently denied the direct link and dissociated himself from public claims that his group had identified a ‘gene for aggression’. Yet the paper is now widely cited, and what was described in its title as ‘abnormal’ now becomes ‘aggressive behaviour.’ Thus a paper describing mice lacking the monoamine oxidase A enzyme, appeared in Science under the title “Aggressive Behaviour” two years after the Brunner paper.

The authors, primarily a French group headed by Olivier Cases, described mouse pups showing “trembling, difficulty in righting, and fearfulness...frantic running and falling over..(disturbed) sleep...propensity to bite the experimenter...hunched posture...” Of all these features of disturbed development the authors chose only to highlight aggression in their paper’s title, and to conclude their account by claiming that these results “support the idea that the particularly aggressive behavior of the few known human males lacking MAOA ...is a more direct consequence of MAO deficiency.”

Such evidence‚ slight though it is‚ has become part of the arsenal employed by, for example, the US Federal Violence Initiative, which aims at identifying inner city children regarded as ‘at risk’ of becoming violent as result of predisposing biochemical or genetic factors. This program, proposed originally by the then director of the US National Institute of Mental Health, Frederick Goodwin, originally ran into a hostility over its potentially racist overtones – ie, repeated coded references to “high-impact inner city” youth. Not long after, Goodwin left his directorship, and proposals to hold a meeting to discuss his proposals were abandoned several times. Nonetheless, aspects of the research program continue in Chicago and other cities.

The example of ‘aggression genes’ could be made over and over again in relationship to many of the other claims to explain the genetic roots of abnormal or undesirable human behavior. Such claims hit the headlines, and now influence social policy initiatives. Yet uncritical attempts to apply biological science to legislation about the human condition, if we are not careful, may lead us back into the dark days of eugenics.