Non-maternal carers (allomothers) are hypothesized to lighten the mother's workload, allowing for the specialized human life history including relatively short interbirth intervals and multiple dependent offspring. Here, using in-depth observational data on childcare provided to 78 Agta children (a foraging population in the northern Philippines; aged 0-6 years), we explore whether allomaternal childcare substitutes and decreases maternal childcare. We found that allomother caregiving was associated with reduced maternal childcare, but the substitutive effect varied depending on the source and type of care. Children-only playgroups consistently predicted a decrease in maternal childcare. While grandmothers were rarely available, their presence was negatively associated with maternal presence and childcare, and grandmothers performed similar childcare activities to mothers. These results underscore the importance of allomothering in reducing maternal childcare in the Agta. Our findings suggest that flexibility in childcare sources, including children-only playgroups, may have been the key to human life-history evolution. Overall, our results reinforce the necessity of a broad conceptualization of social support in human childcare. This article is part of the theme issue 'Multidisciplinary perspectives on social support and maternal-child health'.