“Male disposability” theory, made popular by GirlWritesWhat, is not a proper model to explain how males in specific areas of society may be disadvantaged.  It is a viable model at the population level, but not the individual level, and does not take life history strategies into account, which are crucial to understand male-female sexual selection and the evolution of behaviors often termed “gender roles”.

Male disposability theory posits that females are less disposable than males because they are the limiting factor in population growth, and that males are disposable because a single male is capable of inseminating numerous females.  This makes sense when you consider r-selected species (species that produce numerous offspring and little to no parental care).  However, in K-selected species (species that produce few offspring and provide a great deal of parental care, like humans), male disposability theory falls apart because, at the population level, both males andfemales limit population growth optima.  Males with such life-history strategies typically contribute to the reproductive success of their partners by providing direct benefits such as nest guarding, feeding young, and so forth.  Therefore, if the male in a mating pair were to run off or be eaten, the reproductive success of the pair would be critically compromised.

She does touch on anisogamy a bit as a method to explain why females are more “valuable” to populations, but does not further continue to explain that life-history strategy in humans has evolved to accommodate females due to the massive amount of energy and risk invested in reproduction (9-month incubation periods, risk of maternal mortality during childbirth ect.).  She notes that the importance societies placed on women was necessary for their survival, but neglects to mention that both females and males provide critical services for each other in such survival conditions.  An argument could be made that population growth dynamics have made favored the evolution of a mating system that provisions for females and children due to population dynamics.  But GirlWritesWhat does not mention that such provisioning for both children and mothers is in the best interests of males as well, if said male wishes to propagate his genes over multiple generations.   In short, males have always been important, especially in K-selected species like humans.