Understanding patterns of lethal violence among humans requires understanding some important sex differences between males and females. Globally, men are 95 percent of homicide offenders and 79 percent of victims.2 Sex differences in lethal violence tend to be remarkably consistent, on every continent, across every type of society, from hunter-gatherers to large-scale nation states.
To understand why this pattern is so consistent across a wide variety of culturally and geographically diverse societies, we need to start by looking at sex differences in reproductive biology.
Noting these sex differences in reproductive biology and parental investment is important because they help explain why males tend to engage in more violence than females.10 Aggressively engaging in violent conflict is more likely to reduce a female’s fitness, as it may bring unnecessary danger to her offspring, or cause an injury that may prevent her from reproducing in the future. For a male, however, violent conflict can potentially increase his reproductive success through increases in status,11 or by aggressively monopolizing access to key resources.