These self-reporting participants who had high scores for being kind also claimed to be debonair with the opposite sex, have sex with more people, have more casual sexual partners, and enjoy more frequent sex within a serious relationship.
Honestly, considering these stats are based on "self-reports," I don’t know how much I believe them. I mean, I know I say I have a lot more sex than I actually do. And I know most people would exaggerate the level of self-giving to which they subscribe. The whole thing seems a little fishy to me. I guess we had better hope that these altruistic people are also not LIARS.
From an evolutionary perspective, we may be acting nice in order to get laid
“It appears that altruism evolved in our species, in part, because it serves as a signal of other underlying desirable qualities, which helps individuals reproduce,” says lead researcher Professor Arnocky.
If charity and altruism can be seen as signals that things are going well for the person doing the giving, maybe seeing someone act like a decent human being taps into our primitive mode of selecting strong, healthy partners to reproduce with. maybe the underlying desirable qualities are good health, economic success, overall social desirability… or what the study refers to as "higher mating success."