Monoamine oxidase-A (MAOA) is a brain enzyme which helps mop up neurotransmitters after they’ve done their job.
If they don’ get mopped up, they slosh around in your wet matter and make you crazy.
The trouble (I’ll retract that in a minute) is that there are two types of mopper uppers, depending on your genetics. One type mops up pretty well, the other …. well, it seems you will be prone to violence, fear and probably conservative thinking.
If you have the violent MAOA gene which leaves too many neurotransmitters sloshing around and were abused as a child, your chances of developing anti-social or violent behaviour are a whopping 85%. If you have the gene that is good at mopping up and were also abused as a child, you are nine times less likely to be anti-social or violent. Our courts and jails should take account of this science. They don’t, yet.
Further details at an ABC Radio National talk I gave.
And now the retraction. It’s not “trouble.” It’s part of the wonderful biodiversity of humans. If we were all the same our species wouldn’t stand much of a chance in evolution. The science is still young and the above may prove to be too simplistic. There are millions of biochemical and genetic interactions in our bodies and tracing the network could be impossible (my guess is that the network will be NP-Hard mathematically).
It could also be that the violent gene is closely related to the curiosity gene – Serotonin Reuptake Transporter Polymorphism (5HTTLPR). We certainly need both copies of this gene in the human population. Too curious and you’re dead. Not curious enough and you sit fearfully in the corner all day like a chiropractor or Ayn Rand devotee.
Oh, and the child rearing evidence cited above is a good reason why we need to fund parental leave and more parenting support services.
Kevin McCready
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Kevin McCready 
Where can we find more information on this? It sounds like this should be common knowledge in specific circles.
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