On the simplest level. Direct reproduction is far from the only way to propel your genes. You can never have kids, but lead your ethnic group to win a genocidal war against its neighbours, and will be much more successful at it.

I assumed the gendered usage here was intended, since it's not a poem or a format where character count matters. Unfortunately it's ambiguous without further clarification.

I note you've assumed the poster is male.

The "generic sense" of "men" to mean humans is sexist - blatantly so. It's also quickly becoming archaic, for this reason. Going out of your way to use it, instead of "people" or "humans" or "humanity", is now a statement.