Introduction -- What is "gender based violence" (GBV)? -- GBV harms women and children -- Prevalence of GBV worldwide -- Attitudes to acceptability of GBV -- Trends in GBV prevalence and attitudes -- Patriarchal culture & "gender deviance neutralization" cause GBV -- Effects of female seclusion and nomadic pastoralism on GBV risk -- GBV is associated with childhood socialization -- GBV is bullying: a stronger person hits a weaker person -- GBV and women's earnings -- Alcohol increases the risk of GBV -- GBV may be related to cortisol -- GBV is sometimes a response to stressful temperatures -- We need a global intervention to reduce GBV -- Conclusion