[Leaky Eye]

By not desirable do you mean harmful to reproductive success, or just not helpful?

A trait does not have to make its host more fit, it just has to be fit within its host. A trait that actively makes its host less fit has a hard time.

As for your martyr scenario, I do not believe selection can occur in that fashion. Genetic traits that are helpful to societal productivity exist because they also directly help the carrier. In a society that has a certain concentration of cooperative individuals your survival and reproductive success is helped by also being cooperative. Someone here once posted a really old Dawkins video where he was using the selfish gene and the prisoners dilemma to demonstrate this elegantly.