Abstract:  Altruism is beneficial to its recipients and the whole society. By performing altruistic behaviors, individuals altogether enhance their group function and increase the group’s chance of survival in the face of crisis, which further enable the maintenance and development of the human species. However, altruistic behaviors are costly to the actors per se. It seems that altruists are often put at a disadvantage in survival and reproduction, relative to other individuals, especially to those selfish counterparts. A fundamental problem is, if altruistic behaviors inevitably reduce the fitness of altruists, how come these behaviors were spreading from generation to generation? Scholars, from a range of fields, have built intense interests in this problem, and delivered sustained efforts to solve this puzzle over a lengthy period of time. We proposed a dual pathway model based on the review of representative evolutionary explanations for altruism (i.e. multilevel selection theory and competitive altruism) and recent empirical evidence. From the internal side of an individual, altruism evokes a self-incentive process, facilitating a positive interaction between the actors’ psychological reactions and physiological experiences. Such internal benefits are critical to the altruist’s survival under certain circumstances. From the external side, altruism serves as a signal in interpersonal interactions, conveying information about the actors’ positive quality. Altruistic individuals get an easier access to cooperation opportunities, higher status, and more mate choices in the group, and thus can be benefitted from the long term. Taken together, altruists also reap potential fitness gains from their behaviors through internal and external pathways, beyond delivering direct and tangible benefits to others. Consequently, altruism will not disappear in the process of natural selection but will prevail in human beings. Future researchers could devote themselves to examining altruistic behaviors in a broader framework of mind-body relationships. Altruistic behaviors in the public should also be encouraged in order to create a positive spiral circle of altruism on both intra-personal and interpersonal levels.

Key words:  altruism, self-incentive effect, mind-body relationship, fitness