Figure 2.

Conflict over menopause. (a) Potential for sterility of the MI gene (red), PI gene (blue), and MI and PI combined (black) as a function of age. (b) Intragenomic conflict as a function of age. Before the age t^*P natural selection favours genes that promote fertility both when MI and PI (no conflict). Between the ages t^*P and t^*M natural selection favours genes that promote fertility when MI but sterility when PI (conflict). From t^*M on, natural selection favours genes that promote sterility both when MI and PI (no conflict). To elaborate (a and b) we assume that α = β = 0.1 and μ_m = μ_f = 0.1 and we consider two cases of female-biased dispersal: less female bias when d_m = 0.1 and d_f = 0.4, and more female bias when d_m = 0.1 and d_f = 0.6.