Scientists Overturn Long-Held Theory About Male Competition and Sex
A new model challenges the assumption that biological sex differences automatically drive males to compete harder for mates. The finding suggests that resource scarcity—not sexual dimorphism alone—determines whether males or females evolve aggressive competitive traits, with implications for understanding evolution and potentially rethinking assumptions about innate behavioral differences.
Originaltitel: Anisogamy Does Not Always Promote the Evolution of Mating Competition Traits in Males
<p>Anisogamy has evolved in most sexually reproducing multicellular organisms allowing the definition of the male and female sexes, producing small and large gametes. Anisogamy, as the initial sexual dimorphism, is a good starting point to understand the evolution of further sexual dimorphisms. For instance, it is generally accepted that anisogamy sets the stage for more intense mating competition in males than in females. We argue that this idea stems from a restrictive assumption on the conditions under which anisogamy evolved in the first place: the absence of sperm limitation (assuming that all female gametes are fertilized). Here, we relax this assumption and present a model that considers the coevolution of gamete size with a mating competition trait, starting in a population without dimorphism. We vary gamete density to produce different scenarios of gamete limitation. We show that, while at high gamete density the evolution of anisogamy always results in male investment in competition, gamete limitation at intermediate gamete densities allows for either females or males to invest more into mating competition. Our results thus suggest that anisogamy does not always promote mating competition among males. The conditions under which anisogamy evolves matter, as well as the competition trait.</p><p></p><p></p>