The Genetics of Violence

We, in the 1990ís, are slowly and inevitably being faced with the
sociological and biological implications of impending genetic power. This power
is analytical, in such cases as the Human Genome Project, which will hopefully
succeed in mapping out the genetic code for the entire human genetic composition.
Moreover, this power is preventative and participatory in that it can be, and is
being, used to control the behavior of humans and other animals. This new power,
in the eyes of many, is as risky and potentially hazardous as atomic energy: it
must be treated carefully, used under close supervision, performed under
professional consent and observation, otherwise, people will begin to see this
new genetic power as a dangerous drawback, rather than an advancement of human
One of the most highly contested and objectionable topics of genetic
power is the analysis of crime, violence, and impulsivity. Doubtless, most will
agree that children are not born with a natural affinity for violence and crime;
yet, new genetic studies are beginning down a long road of finding the
hereditary basis for impulsivity. While these studies continue to search for the
genetic source of aggression, child testing programs, drug manufacturers, civil
rights activists, lawyers, and anxious citizens await the resulting testimony of
the scientists. The social implications of the genetic search for aggressive
tendency is seen by some as a great step forward, by others as a dangerous power
with the ability to give birth to another Holocaust, and by still others as
At one time, it was believed that oneís character could be determined
from the bumps in oneís skull. Much later, in the 1960ís, as science marched on
in its regular pace, it was theorized that carriers of an extra Y (male)
chromosome were predisposed to criminality. Today, we are faced with the power
to determine and alter oneís character through genetics. We must collectively
decide whether the ultimate price, not of money but of natural evolution, is
worth the ultimate result.

Behavioral Genetics and Aggression
One day in 1978 a woman entered the University Hospital of Nijmegen, the
Netherlands, with complaints regarding the men in her family. Many of the men
seemed to have some sort of mental debility, including her brothers and her son.
In time, a pattern of strange behavior of the men emerged: one had raped his
sister, and, upon being institutionalized, stabbed a warden in the chest with a
pitchfork; another tried to run over his boss in an automobile after he had
criticized the manís work; a third had a regular habit of making his sisters
undress at knife point, and two more were convicted arsonists. Additionally, the
known IQís of the men were typically around 85. The history of this sort of
behavior was found to be typical, as nine other males in the family, tracing
back to 1870, had the same type of disorder. It became evident that there was
something wrong in the lineage of the family. Hans Brunner, a geneticist at the
University Hospital, has been studying the family since 1988.
It was discovered that the men had a defect on the X chromosome that
helps regulate aggressive behavior. Brunner was cued to the fact that the defect
was on the X chromosome because the trait was passed on from mother to son, and
none of the women, with two X chromosomes, were afflicted. The gene normally
codes for the production of the enzyme monoamine oxidase A (MAOA), which breaks
down three important neurotransmitters that trigger or inhibit the transmission
of nerve impulses. One of these neurotransmitters is norepinephrine, which
raises blood pressure and increases alertness as part of the bodyís "fight or
flight" mechanism. Brunner believes that the lack of this neurotransmitter
could cause an excess of chemical messages to the brain, in times of stress,
causing the victimís fury. The menís urine found extremely low levels of the
breakdown products of the three neurotransmitters, which are the breakdown
products after MAOA has done its work.
Another of the chemicals is serotonin, which inhibits the effects of
spontaneous neuronal firing, and consequently exerts a calming effect. The lack
of this inhibitor is held responsible for the "Jekyll and Hyde" personalities of
the afflicted men, and may be responsible for their low IQís.
Over the course of four years, Brunner was the first to ever link and
pinpoint a single gene to aggression. Also, he analyzed the X chromosomes of 28
members of the family, compiling sufficient evidence to prove his discovery.
However, Brunner never studied the influence of a shared environment on the men.
Many other factors of genetic and biochemical signals have