Pair-bonding, fatherhood, and the role of testosterone: A meta-analytic review

•The Challenge Hypothesis (CH) concerns the dynamics of male life-history strategies.•The CH predicts that testosterone (T) mediates shifts between mating and parenting.•In humans, pair-bonding and fatherhood generally correspond to lower T.•We meta-analyze 114 effects to quantify magnitudes of predicted CH effects in men.•We find both robust effects and evidence of selective reporting. Males of many species must allocate limited energy budgets between mating and parenting effort. The Challenge Hypothesis provides a framework for understanding these life-history trade-offs via the disparate roles of testosterone (T) in aggression, sexual behavior, and parenting. It predicts that males pursuing mating opportunities have higher T than males pursuing paternal strategies, and in humans, many studies indeed report that men who are fathers and/or pair-bonded have lower T than childless and/or unpaired men. However, the magnitude of these effects, and the influence of methodological variation on effect sizes, have not been quantitatively assessed. We meta-analyzed 114 effects from 66 published and unpublished studies covering four predictions inspired by the Challenge Hypothesis. We confirm that pair-bonded men have lower T than single men, and fathers have lower T than childless men. Furthermore, men more oriented toward pair-bonding or offspring investment had lower T. We discuss the practical meaningfulness of the effect sizes we estimate in relation to known factors (e.g., aging, geographic population) that influence men’s T concentrations.