Perpetrators of violence and homicide had something in common: they were young, single and didn’t have access to the kinds of resources with which to win mates. Polygynous societies in which wealthier men have access to multiple women are more violent and less stable because they have a class of young men without the prospect of getting a mate. Monogamy, rather than being the state of nature, may have been an important cultural technology for reducing violence.
Diana Fleischman writes about sex robots and connections between sexual behavior and violence. (link)