LAUSR

Ultimate and proximate explanations of men’s physical intimate partner violence (IPV) against women have been proposed. An ultimate explanation posits that IPV is used to achieve a selfish fitness-relevant outcome, and predicts that IPV is associated with greater marital fertility. Proximate IPV explanations contain either complementary strategic components (for example, men’s desire for partner control), non-strategic components (for example, men’s self-regulatory failure), or both strategic and non-strategic components involving social learning. Consistent with an expectation from an ultimate IPV explanation, we find that IPV predicts greater marital fertility among Tsimané forager-horticulturalists of Bolivia (n = 133 marriages, 105 women). This result is robust to using between- versus within-subject comparisons, and considering secular changes, reverse causality, recall bias and other factors (for example, women’s preference for high-status men who may be more aggressive than lower-status men). Consistent with a complementary expectation from a strategic proximate IPV explanation, greater IPV rate is associated with men’s attitudes favouring intersexual control. Neither men’s propensity for intrasexual physical aggression, nor men’s or women’s childhood exposure to family violence predict IPV rate. Our results suggest a psychological and behavioural mechanism through which men exert direct influence over marital fertility, which may manifest when spouses differ in preferred family sizes.A study of intimate partner violence among the Tsimané forager-horticulturalists of Bolivia finds evidence that male aggression is leveraged to increase marital fertility and a man’s individual fitness when spouses differ in preferred family size.