Hungarian researchers challenge Darwin’s theory about sexual selection

Researchers from the ELKH Centre for Ecological Research and the University of Debrecen have recently published a study in the international multidisciplinary journal Scientific Reports. They claim that the Darwin–Bateman paradigm, according to which sex differences originate in differences in size and/or function of gametes, can only be partially supported by life-history trait data and their results question a key assumption of the 150-year-old paradigm.

Sex roles, i.e. behavioural and physiological differences between males and females, are common in reproduction. The debates about the evolutional origin of sex roles date back to Charles Darwin, the father of the theory of evolution, writes ELKH.

The Paradigm

150 years ago, he discovered that inter-and intrasexual competition is important for natural selection. In the process of intrasexual selection, same-sex animals compete to get the best or most mates. Intersexual selection results from interactions between the sexes, and it involves sex differences in parental care and morphological traits.

Sexual selection takes place at many levels, but the goal is always to produce more high-quality offspring by minimising energy investment. Therefore, most species try to get away with providing the least amount of care to their offspring. This often results in one parent, typically the male, providing less parental care.

According to the Darwin–Bateman paradigm, differences in size and/or function of gametes between the sexes (male gametes tend to be small and motile, while female gametes are usually larger and sessile) lead to biased sexual selection and sex differences in parental care and body size.