17 December 2012

Oh, Those Violent Genes! Genetic Landscapes of Violence

There are neighborhoods that you know to avoid, if you want to keep your wallet, your vehicle, your life, and any loved ones who accompany you. Likewise, there are entire cities, countries, and regions of the world which intelligent people will only visit for very good reason -- accompanied by ample protection.

If one makes the association between the human makeup of such neighborhoods, cities, countries -- and the people who inhabit those places -- one is apt to be labeled a "racist" in the worlds of politically correct groupthink.

But when the modern scientific worlds of genetics and cognitive science come together and declare an association between particular gene sets, and specific types of violent behaviours, intelligent people are given a glimpse behind the curtain of political correctness, into the grist and blood of an important underlying reality.

The flow chart of violence above is taken from the article "Genes for susceptibility to violence." It provides a glimpse at some of the different factors which may contribute to the decision (conscious or unconscious) to commit violent acts. The MAO-L genotype refers to the specific monoamine oxidase A (MAO-A) promoter variant which is at least 10 times more common in people of African descent than in most other population groups, and which seems to predispose to both violence and antisocial disorders.

The MAO-L genotype is not the only gene variant which may predispose to violent behaviours, as you can see below:
The table above looks at a number of gene variants which have been associated with violent and other antisocial behaviours. It was taken from an article first published in : Aggression and Violent Behavior 14 (2009) 286–294.

The full set of genetic factors which play into violent behaviour will not be compiled for quite some time yet. Since we have barely discovered the underlying genetic foundations of impulse control, intelligence, executive function, cognitive assessment of threat, susceptibility to fear conditioning, etc., it will take a number of decades to fill in the outlines -- and much more to fill in the gaps.
The excerpt above comes from the summary of the article "Natural Born Killers: The Genetic Origins of Extreme Violence." It is meant to help explain the difference in rates of violence between men and women. The reference to "impulse control" makes an important point: Even humans who are genetically predisposed to anti-social behaviours can exert self-control to abort impulses toward violent behaviours before they are carried out.

And since "impulse control" itself is largely genetically determined, we see that if an individual is genetically inclined to harbour violent impulses -- and is additionally genetically inclined to have low impulse control -- the likelihood of that person exhibiting violent behaviours is much higher than in a person who exhibited only one of the two genetically determined traits.

Parenthetically, blacks typically display lower levels of impulse control than other population groups.
The image above was first published in The Journal of Social Psychology, 2010, 150(2), 160–180. PDF download of article.

The catalyst model of violence was devised by violence researcher Christopher Ferguson. It attempts to illustrate the multiple factors -- genetic and environmental -- which come together to generate violent and anti-social behaviours.

The image suggests a one-way flow from predispositions on the left, to violent behaviours on the image far right. But the actual processes involved -- genetic, emotional/cognitive, and environmental -- are far more complex, with multiple circular feedback loops interacting with each other.

If one looks at the geographical map of violent crime, it is easy to infer that genetic factors -- probably many genetic factors -- interact to cause higher rates of violence among African-derived populations.

Blacks have higher genetic prevalence of some of the factors that predispose to impulsive violence, are genetically inclined to have lesser control of these impulses -- both in terms of executive function and IQ. As the complex components of violence are further uncovered, we will learn more about the reasons for the large discrepancies in rates of violence between African-derived populations, and other human populations.

For although the PC groupthink police will tell you that it is racist to think about such things, in the real world understanding these differences may save your life, and the lives of people you care about.

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