many species have different male morphs that pursue different evolutionary strategies. well-known examples are those birds, where males can be either big and territorially dominant or small and impersonating females to stay on the larger ones territory, or fish where the small male morph will quickly swim up and blast his semen over the females eggs while she's mating with another large male.
the cause of this can be regions of the genome that are in extreme linkage disequillibrium with each other, meaning multiple genes are basically inherited as a unit, since the selection against any incomplete combination is so strong, say dominant small male.

what if this is true for men too, with some men being mentally alphas with big dicks, and other men being mental betas with small dicks. the alpha pursues an evolutionary strategy based on attraction, whereas the beta pursues an evolutionary strategy based on being the comfort option of the woman. he has a small penis so that the woman will have sex with him even while being sore from the alphas big penis.