Helping those who help others: The roles of indirect reciprocity and relatedness

“Helping those who help others” appears to be a widespread phenomenon. It is typically framed as indirect reciprocity in which individuals who are seen to help later receive returns from third parties. Here, I propose that helping can also be explained by the benefits that result from helping related helpers (where relatedness means sharing genes more than average, whether due to genealogy or some other mechanism). I test the functional roles of relatedness (or “kin selection”) and of reciprocity in explaining helping by varying the population structure and the number of interactions in individual-based simulations. First, with a unitary population in which individuals had a greater tendency to meet others of their own type, there were high levels of a discriminating strategy which helped other helpers. This can be explained by kin selection, in which helpers who help other helpers increase the payoff of their own strategy despite incurring a cost themselves. Introducing an “island population” structure reduced these indirect fitness benefits from helping, and this caused the frequency of the discriminating strategy to decrease markedly. Finally, increasing the number of interactions caused only a small increase in the level of the discriminating strategy (and thereby of helping helpers), consistent with indirect reciprocity (by means of the simplest strategy) being very weak. I argue that relatedness requires greater attention as an alternative to indirect reciprocity in explaining why individuals might help those who help others.