Obligate sex in animals is puzzling because it's hard to understand why populations resist switching to a mix of sexual and asexual reproduction. Sexual conflict and mate availability play a role in determining how different reproductive strategies evolve. Through computer models, researchers found that a mutant gene allowing females to reproduce asexually can spread in a population even if males try to stop it. This mutant gene benefits from producing some offspring asexually before encountering males. The spread of this gene is influenced by factors like the ratio of males to females and the genetic link between different genes. Overall, the study suggests that the genetic makeup of animals can promote the maintenance of sexual reproduction, even when asexual reproduction seems advantageous.