Why don't men do more to help raise their children?
This question isn't taken from a women's weekly, it's an evolutionary teaser given to undergraduate biology students. Humans are monogamous, on the whole, forming long-term relationships in which males contribute to the care and protection of their offspring. But they could still do more, and I don't mean just changing the baby's diapers at 3 a.m. Men have nipples, for example, but they don't breast-feed. Why not?
Because most of the energy that males of almost all species allocate for reproduction gets spent on attracting and winning mates, that's why not. Most of the energy that females spend on reproduction goes toward nurturing and caring for their offspring. Maybe it's not worth it, evolutionarily speaking, for men to suckle their offspring.