The predicted effect of increasing status competition on fertility with a shift from pre- to post-demographic transition ecological conditions. We hypothesize that fertility falls across the demographic transition not only due to an increase in the gains to direct investment in productivity, but also due to an increase in investment in status competition. The grey curve shows the effect of increasing gains to direct investment in productivity alone. The dashed black curve shows the additional effect of increasing inequality in the inputs to status, while the solid black curve shows the additional effects of increasing both inequality and the intensity of status competition. (The gains to direct productivity investment are assumed to increase for all three curves. For simplicity, other factors that we recognize as important, such as reduced infant mortality rates, are not explicitly modelled. See the electronic supplementary material for a description of the model parameters used to generate this plot.)