Gautam Naik provides an interesting and cleverly written piece on the search for a biological basis of violent behavior.
If you want to have fodder for controversial cocktail conversation, take a look also at an old book by James Q. Wilson and Richard Herrnstein on the biology of criminal behavior.
(Hat tip: Daniel Lippman)
and 
. You can also watch it on 
CAM @5:
You assert this notion of “choosing”, but there is little or no evidence to support the claim that we choose at all. In fact, the data before you undermines the notion of a free choice. If a group of people with a certain gene or set of genes tend to make one choice more often than another group with different genes, it starts to look less like a free choice. Further, even environmental effects (like how you were raised) do not suggest choice. That is, you don’t choose who raised you or how and you don’t choose your genes. Thus, when those two factors predict your behavior (even if not perfectly), why would you claim the resultant outcome is the result of anything we would recognize as choice?
I would recommend Randall Collin’s microsociological study, On Violence. Yes, there is a genetic component; it’s what makes for naturally talented killers such as Mafia hitmen and Alvin York (WWI pacifist war hero). But in ordinary life, it’s social situations and human agency that has a much bigger impact on whether an interaction devolves into violence.
This is an outdated theory first proposed by Lombroso. It is nice to see that modern shamans play same games.