Producing breast milk is very expensive in terms of the energy it requires. From an evolutionary perspective, unless it significantly benefits the survival of a species, male lactation really isn’t worth the cost. For most mammals, evolution has shown that the best way to perpetuate the species is when the female invests in nurturing while the male concentrates on attracting females and spreading their seed.

Scientists still don’t fully understand all the factors that influence the production of milk. It’s definitely known that this doesn’t just have to do with the physical structure of the breast, but also with the different levels of various hormones in the blood stream that fluctuate in response to a suckling stimulus. Even in cases when lactation has been artificially induced, the mother doesn’t always produce a full supply of milk.