Googled around a bit and found an article trashing the warrior gene as inconclusive.   Unfortunately it partly does so by saying attributing any behavior to a particular gene is too simple to be true.  In my defense ‘Ancient Breed’ and the civilization gene stems from social/economic observation not genetics, AND I have contended that it could be a small group of rapid succession mutations (though I doubt it.)

http://www.genome.duke.edu/seminars/journal-club/documents/Yong2010.pdf

This is the really interesting part.  I have contended that while conflict actually helps empaths grow (by building useful emotional metadata) that it damages psychopaths.  Particularly if they can’t get relief from their negative environment so they can quietly build their logical understanding of what just happened.    That logical growth, and the explosion that can follow the lack of it,  is why psychopaths need social isolation.  The kind of social isolation like you can obtain living like a hermit or that you can buy with vast wealth.

Now that I’ve front loaded the hell out of you, here is the quote.

“A third of these men carried the MAOA-L variant.  Now, aged 26, this group was indeed more likely than the others to have developed antisocial disorders and violent behavior – but only if they had been poorly treated or abused as children.  Moffitt and Caspi concluded that the so-called “warrior gene” affects a child’s sensitivity to stress and trauma at an early age.  Childhood trauma “activates” bad behavior, but in a caring environment it’s effect is quashed.”

Here was Ed Yong’s blog in discover
http://blogs.discovermagazine.com/notrocketscience/

And here it is in nat geo (which seems broken today)  http://phenomena.nationalgeographic.com/blog/not-exactly-rocket-science/

And the permalink to the article (PAYWALL)
http://www.newscientist.com/article/mg20627557.300-dangerous-dna-the-truth-about-the-warrior-gene.html