reciprocal altruismyoudaoicibaDictYouDict[reciprocal altruism 词源字典]
"Behaviour that benefits another unrelated organism, carried out in the expectation of its being reciprocated; the theory holding that behaviour of this type has evolved because is likely to increase the chances of survival or reproductive success for the apparently altruistic organism", 1970s.[reciprocal altruism etymology, reciprocal altruism origin, 英语词源]