The Theory Of Replaceability: An Evolutionary Mechanism Influencing Differential Variability In Dimorphic Species

This paper proposes a new theory, the 'Theory of Replaceability', to address the long-standing question of why one sex may evolve with greater variability than the other. The theory posits that if the survivability of offspring and the species as a whole depends disproportionately on one sex, natural selection will favor the minimization of variability in that sex, which it perceives as 'less replaceable.' This ensures the stability of traits crucial for reproductive success and population continuity. In contrast, the 'more replaceable' sex is treated as a lower-risk substrate for evolutionary experimentation, driven by the lower costs associated with the loss or impaired function of its individuals. Consequently, this sex may experience relaxed stabilizing selection, allowing a greater range of mutations and variation to arise and persist, ultimately leading to its increased phenotypic diversity. This differential allocation of risk offers a compelling explanation for the patterns of variability observed across many dimorphic species.