Why Do Males Exist? Sexual females produce both sons and daughters, while asexual females make only daughters. Because only females produce offspring, this "cost of males" predicts that sex should be rare because asexual females will leave many more descendants than will sexual females. In reality, however, sex predominates. Why sex is so common despite its costs remains unclear, and is considered one of the most important unanswered questions in evolutionary biology. Because sex is distinguished from asexual reproduction by the production of genetically variable offspring, a better understanding of the benefits of sex is also of direct relevance to understanding the value of preserving genetic diversity within and among populations, species, and ecological communities.

How Are Sexuals and Asexuals Different? The expectation that sex should be rare is based on the assumption that sexuals and asexuals are similar. In other words, the two-fold cost of sex will be diminished or even negated if asexual females experience disadvantages related to asexuality. Accordingly, our research uses a variety of approaches to identify and understand the consequences of the many ways in which asexuals and sexuals might differ, with the goal of better understanding why sex is so common in natural populations.