Metrics details. An evolved preference for other-regarding or helping behaviour in potential mates has been proposed as an additional mechanism by which these behaviours can yield direct fitness benefits in humans. We asked 32 heterosexual women and 35 heterosexual men to rate the attractiveness of members of the opposite sex in the presence and the absence of information about helping behaviours.
Reports of helping behaviour were associated with a significant increase in the attractiveness of both men and women as potential long-term sexual partners. Altruism also increased the attractiveness of men as potential partners for short-term flings, but to a lesser extent than when the same men were being considered for long-term relationships. Altruism did not affect the attractiveness of women as partners for short-term flings.
Our results unite two important areas of evolutionary theory — social evolution and sexual selection — and extend the list of means by which helping behaviours, which appear at first glance to be costly to the actor, can in fact earn direct fitness benefits.
Exactly why helping behaviours in a non-mating context might be attractive to potential mates, and whether they are honest signals of mate quality, remains to be elucidated. Such behaviours can earn direct fitness benefits as a result of mutual benefit, reciprocity, evasion of punishment or enhancement of social status, as well as indirect kin-selected fitness benefits reviewed in [ 2 — 4 ]. An evolved preference for other-regarding behaviour in potential mates has been proposed as an additional mechanism by which helping behaviours can yield direct fitness benefits in humans [ 5 — 8 ].
This hypothesis has not yet received the level of empirical attention paid to other mechanisms by which helping behaviours earn direct fitness benefits. An evolved preference for helping behaviour in mates is predicted to arise when parents need to cooperate to raise offspring successfully. The incidence of biparental care across the tree of life is sparse, but it is common in birds [ 9 ] and canids [ 10 ] and is practised by a significant minority of cichlid fishes [ 11 ] and primates [ 12 ], including humans.
