This contribution investigates the role ofworking time in the course of agricultural development. In so doing, we revisit Ester Boserup’s (1965, 1981) hypothesis of increasing land productivity at the expense of declining labour productivity as a consequence of agricultural intensification in subsistence communities. We introduce a theoretical framework that centres on human time as a ‘limited’ biophysical resource and compare the labour burden across gender and age of four subsistence communities, one each from India, Bolivia, Nicaragua, and Laos. While Boserup’s claim applies to early stages of agricultural development, we find the dynamics to change with the introduction of fossil fuel based inputs into agriculture, leading to a rise in labour productivity. Despite these improvements, we still find overall labour needs to increase with agricultural intensification. Since household labour remains largely constant during the development process, the labour burden is primarily borne by women.