Résumé
The Darwin-Bateman paradigm advanced as the central concept to explain the
evolutionary origin of sex differences. However, debates regarding its
theoretical underpinnings persist, particularly with respect to the role
of anisogamy in sexual selection. The theoretical work presented by
Lehtonen and Parker (2024) suggests that the initial split in gamete
production rate drives sex differences in sexual selection but that any
further variation in the degree of anisogamy is not expected to alter the
strength of sexual selection in males and females. Here, I discuss the
historical background of a recently emerged controversy and present
empirical data that corroborate the theoretical predictions. Lehtonen and
Parker’s contribution refines our understanding of the Darwin-Bateman
paradigm by providing a broad theory for large-scale patterns of sex
differences that can be observed in nature. Further understanding of how
demographic and environmental factors influence sexual selection is
essential to predict the vast diversity of sex differences across the tree
of life, beyond the primordial impact of anisogamy.