Thirty Years of the Biology of Spermatozoa: The Rise and Future of an Evolutionary Paradigm.

In the early 1970s, Geoff Parker recognised that because females frequently mate with multiple males, competition for fertilizations will impose significant sexual selection on males and their ejaculates. Post-mating sexual selection has since developed into a significant evolutionary paradigm, in no small part fostered by the biennial meeting of the Biology of Spermatozoa (BoS) community. BoS celebrated its thirtieth anniversary in 2025, prompting reflection on the development of the discipline and its future. The paradigm has shifted from one focused predominantly on competition among males for fertilizations to a holistic appreciation of the role of females and ova in determining fertilisation success, and the interacting effects of males and females on fertilisation outcomes. The field has transitioned from a phenotypic focus to one in which omics are yielding unprecedented insight into the biology of sperm, ova and male and female reproductive fluids that affect fertilisation dynamics. Understanding sperm biology has become a strongly interdisciplinary venture, fostered by the BoS meetings. Key discoveries over the last 30 years are highlighted and areas for future development identified. The history of this field highlights the critical role played by small, focused meetings and workshops.