The intentional killing of someone in which the perpetrator and victim are the same-sex, that is, both are male, or both are female.
There are four combinations of perpetrator-victim relations by sex: men killing men, men killing women, women killing men, and women killing women. The proportion of homicides that occur in each of these categories is not equal, contrary to the expectation when random occurrence is hypothesized in large populations. Rather, the majority of homicide cases consist of men killing other men. When you look specifically at same-sex homicide, male-male homicide occurs much more frequently than female-female homicide, especially between unrelated persons, across many different societies and cultures, and spanning long periods of time (Daly and Wilson 1988). This entry will discuss an evolutionary explanation for this phenomenon.
Violence and Sexual Selection