Conformity and content-biased cultural transmission in the evolution of altruism

The evolution of altruism has been extensively modeled under the assumption of genetic transmission, whereas the dynamics under cultural transmission are less well understood. Previous research has shown that cultural transmission can facilitate the evolution of altruism by increasing (1) the probability of adopting the altruistic phenotype, and (2) assortment between altruists. We incorporate vertical and oblique transmission, which can be conformist or anti-conformist, into models of parental care, sibling altruism, and altruism between individuals that meet assortatively. If oblique transmission is conformist, it becomes easier for altruism to invade a population of non-altruists as the probability of vertical transmission increases. If oblique transmission is anti-conformist, decreasing vertical transmission facilitates invasion by altruism in the assortative meeting model, whereas in other models, there is a trade-off: greater vertical transmission produces greater assortment among genetically related altruists, but lowers the probability of adopting altruism via anti-conformity. Compared to conditions for invasion under genetic transmission, e.g., Hamilton's rule, we show that invasion can be easier with sufficiently strong anti-conformity, and in some models, with sufficiently high assortment even if oblique transmission is conformist. We also explore invasion by an allele A that increases individuals' content bias for altruism, in the absence of other forms of cultural transmission. If costs and benefits combine additively, A invades under previously known conditions. If costs and benefits combine multiplicatively, invasion by A and by altruism become more difficult than in the corresponding additive models. (C) 2021 The Author( s). Published by Elsevier Inc.

Automated summary

The evolution of altruism has been extensively studied under genetic transmission, but less is known about its dynamics under cultural transmission. Previous research has shown that cultural transmission can facilitate the evolution of altruism by increasing the probability of adopting altruistic behavior and promoting assortment among altruists. This study incorporates vertical and oblique transmission, and explores the effects of conformist and anti-conformist transmission on the evolution of altruism in different scenarios. It also investigates the invasion of an allele that increases individuals' content bias for altruism in the absence of other forms of cultural transmission.