The Cultural Evolution of Indiscriminate Altruism in a Large Randomly Matching Population

Altruism is hard to explain because altruistic acts are costly to the individuals who perform them. Although past work has identified conditions under which altruism can evolve, there is wide agreement among evolutionary theorists in the social sciences and biology that indiscriminate altruism cannot evolve in a large randomly matching population. Building on earlier work (Mark, 2002), I show that cultural transmission can create a cultural evolutionary force toward indiscriminate altruism in a large randomly matching population. The cultural transmission of a behavior (altruistic or selfish) disproportionately exposes those who acquire that behavior to that behavior prior to its acquisition. That is, individuals who have acquired an altruistic behavior through cultural transmission (i.e., who learned to behave altruistically from other people) were disproportionately exposed to the altruistic acts of others. Likewise, individuals who have acquired a selfish behavior through cultural transmission were disproportionately exposed to the selfish acts of others. Because of this disproportionate prior exposure, altruists have disproportionately benefitted from the altruistic acts of others, and selfish individuals have disproportionately been hurt by the selfish acts of others. If the benefits of being the target of altruistic acts increase one's attractiveness as a behavioral model, then a cultural evolutionary force toward altruism results.