A similar conclusion can be had by considering unselfishness.

As used here, a person is "unselfish" if he/she sees himself/herself as a part of a larger thing that he/she lives to serve. A selfish male can couple with a selfish female, and they can use each other and enjoy the pleasures of reproduction. Such a relationship will be conditional (transactional), except to the extent that hardwired (instinctive) emotional bonds form. A selfish male can couple with an unselfish female, or vice versa, but in such a relationship the unselfish mate will be destroyed and the couple is not likely to reproduce successfully. Only when an unselfish male couples with an unselfish female is it possible for the relationship to be unconditional. But it won't work if the larger thing that the male lives for is not the same as the larger thing that the female lives for. Only when they are both giving of themselves entirely to the same larger thing can it work.