The Science of Evil by Simon Baron-Cohen

The Science of Evil by Simon Baron-Cohen

Author:Simon Baron-Cohen
Language: eng
Format: mobi, epub
Publisher: Basic Books
Published: 2011-04-19T10:00:00+00:00


Genes for Aggression

Some scientists have focused their search for empathy genes on those that affect the neurotransmitter serotonin. Too much serotonin in the synapse has been linked to aggression. When you increase serotonin receptor activity, which clears serotonin from the synapse, this decreases aggression.282 An example of a gene involved in clearing serotonin (and other neurotransmitters such as dopamine, noradrenaline, and adrenaline) is the MAOA (monoamine oxidase-A) gene.

Now here’s the interesting bit. There are several forms of this gene. One is called MAOA-L because carriers of this gene produce low (L) levels of a key enzyme. The other form of the gene is called MAOA-H because carriers produce high (H) levels of the same enzyme. Low levels of MAOA often mean high levels of neurotransmitters in the synapses. Not surprisingly, people with the MAOA-H form are less aggressive. People with the MAOA-L form are overrepresented in warrior cultures (such as the Maoris in New Zealand). For this reason, controversially, it has been called the “warrior gene.” It won’t surprise you that this gene interacts with environmental factors. For example, Avshalom Caspi and his colleagues found that abused children with the MAOA-L form of the gene were more likely to develop antisocial problems compared to abused children with the MAOA-H form of the gene.283,284

Animal research backs this up: Male mice with a deletion of the MAOA gene show more aggressive behavior. In humans, male members of a Dutch family with a mutation of the MAOA gene showed high levels of aggression. And neuroimaging reveals the amygdala and the anterior cingulate (two key regions in the empathy circuit) are smaller in MAOA-L carriers. Carriers of this version of the gene also show increased amygdala and reduced anterior cingulate activity when matching facial expressions.285,286



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