Sexual reproduction is one of the most fascinating biological phenomena, and the resulting sexual selection and sexual conflicts are probably responsible for the most attention-grabbing phenotypes in nature, such as the arresting colours and shapes of flowers, the pleasing and elaborate songs of birds, the massive horns of some deers and beetles, and the often intricate and bewildering genital morphologies of internal fertilizers.
It is hard to imagine how infinitely less exciting life would be without sex; but even more striking is that we still lack a coherent theory of why sex is so wide-spread, a conundrum that it is on a par with other great biological mysteries, such as why many organisms sleep, age, and have stem cells, or why there are so many species.
Although our understanding of the origins of sex and its evolutionary consequences has flourished since Darwin planted the crucial theoretical seeds, it is important to realize that this research has been extremely biased. Most work has focussed on separate-sexed animals, and relatively little work has investigated either hermaphroditic animals and plants, or the baffling diversity of sexual systems in fungi and other eukaryotic groups, leaving sex poorly understood in a large part of the tree of life.
This taxonomic and conceptual bias clearly prevents the establishment of a general evolutionary theory of sex, and current definitions and mathematical formalizations of key concepts often just presuppose the existence of males and females, and frequently also the roles these play in reproduction. In spite of these biases, researchers hope to establish the general patterns, an endeavour that is bound to fail. Our research therefore aims to understand the evolutionary biology of sexual reproduction in one of these poorly studied groups, the hermaphroditic animals, and we strive to conceptually unify our work with that done on other sexual systems wherever possible.