Interspecific sexual selection, a new theory for an old practice: the increase of artificial biodiversity through creation of modern, standardized breeds

Abstract

Darwin set the pillars of organismic evolution when he defined natural and sexual selection in the 19th century. Concurrently, a frenzy of selective breeding programmes, generally supported by the wealthy and aristocratic, gave rise to novel breeds of plants and animals at a rate that was previously unforeseen. Since then, breeds selected over millennia and adapted to local conditions began to disappear or were threatened with extinction, being substituted by these new, standardized breeds. It is of interest to explore how new breeds emerged and what the main criteria of the founders of these breeds were. Darwin seemed to be unaware that his contemporaries were practicing a form of interspecific sexual selection responsible for the fixation of exaggerated traits, often plainly ornamental, in the new breeds they intended to create. Parent animals were chosen by individuals who were following particular goals, often with aesthetic criteria in mind. Here we investigated who were the founders of modern breeds in five domesticated species (dogs, cats, pigs, horses and cattle), as very often a single person is credited with the creation of a breed. We found information on founders of 459 breeds, 270 of which were created after 1800. Interestingly, for these species, breed creation is overwhelmingly attributed to men. In the wild, however, the choice of mate is usually performed by the female of a species and thought to be adaptive. Breeders in the Victorian era, nevertheless, lacked such adaptive skills and had little scientific knowledge. The selection of individuals with an extreme expression of the desired traits were often close relatives, resulting in high inbreeding and a variety of genetic disorders.