Gender differences in violence are a function of brain neurotransmitters
It could be argued, I suppose,
that women are not « really » more docile than men. It could be argued that women are
acculturated into docility, doing
themselves violence by forcing themselves, and being forced, into docility, against
their true nature. Here is the evidence
to the effect that men are « really » more violent than women because
of endogenous differences in their brains.
Dopamine seems to be more concentrated and more active in men’s than in
women’s brains (though there are some local exceptions). Brain serotonin, on the other hand, seems to
be less present in men than in women. The same pattern of sex differences is
observed in monkeys, dogs, wolves, rats, birds and fish (Augustinovich, 1992;
Saudou et al, 1994). Wild versions of animals (wolves,
buffalo) have the human male pattern whereas domestic versions of the same
species (dogs, cattle) have the female human pattern. Artificial selection of
these species (breeding) had the obvious objective (among other things) of
producing strains that could adapt to domestic life. Breeders certainly selected animals which
were docile around humans. By having
them mate with similar animals, the
breeders ended up fixing in successive generations those genes responsible for
the desired behavioral and physical traits.
And it seems extremely likely that the genes in question influence
synthesis of selective neurotransmitters.
Serotonin-deficient animals are more aggressive than their normal
counterparts (Sluyter
et al, 1996). Pro-serotonin and antidopaminergic
manipulations have a pacifying effect in various species studied so far (Arregui et al, 1993; Bernhardt, 1997; Pant et Nath,
1993). Homicide victims are often
people with records of violent crime.
One can confidently suppose that they are more aggressive than people
who die of more natural causes. Brains
of homicide victims have been intensively studied. They are generally deficient in serotonin
and overly endowed in dopamine (Ohmori, Arora & Meltzer, 1992). Extremely aggressive men,
psychopathic criminals, have an exacerbation of the male-typical pattern. A recent epidemiological study investigated
a very large cohort of 781 normal men and women with regard to whole blood
serotonin and violence. A highly
significant relation was found between high serotonin levels (which the authors
assume to correspond to low brain levels) and violent behavior, in men.
Another recent study even found that post menopausal women with lower
serotonin levels manifested more impulsivity and hostility than women with
higher levels of serotonin. This
finding was not found in pre menopausal women presumable because the menstrual
cycle made women too « variable » to yield a reliable correlation
(Manuck et al, 1998).
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