In our prehistoric past, we would have lived in extended families, surrounded by kin whose interests we might have wanted to promote because they shared our genes. Now we live in big cities. We are not among kin nor people who will ever reciprocate our good deeds. It doesn't matter. Just as people engaged in sex with contraception are not aware of being motivated by a drive to have babies, it doesn't cross our mind that the reason for do-gooding is based in the fact that our primitive ancestors lived in small groups.