Original ArticleThe evolution of costly displays, cooperation and religion: credibility enhancing displays and their implications for cultural evolution
Introduction
Researchers from across the behavioral sciences have long proposed a connection between apparently costly displays — often in various ritualized forms such as firewalking, ritual scarification, animal sacrifice and subincision — and deep levels of commitment to group ideologies, religious beliefs and shared values that promote solidarity and in-group cooperation (Atran and Norenzayan, 2004, Cronk, 1994, Durkheim, 1995, Irons, 1996, Rappaport, 1999, Sosis and Alcorta, 2003). This paper provides a novel approach to understanding these observations by considering how natural selection might have shaped our cognitive processes for cultural learning so as to give salience to certain kinds of displays or actions, and what the implications of such cognitive processes are for cultural evolution. Since my goal is merely to get this approach on the table, where it can compete with alternatives, I aim to provide a prima facie case for considering these ideas, and not a set of conclusive tests.
The argument proceeds in three parts. Part I lays out a theory for the evolution of one particular component in the suite of cognitive adaptations that make up the human capacity for cultural learning. The core idea is that, with the evolution of substantial communicative capacities in the human lineage, cultural learners are potentially exploitable by manipulators who can convey one mental representation but actually believe something else, or at least misrepresent their depth of commitment to a particular belief. To address this adaptive challenge, I propose that learners have evolved to attend to credibility enhancing displays (CREDs) alongside the verbal expressions of their models (i.e., those individuals from whom people learn). These displays provide the learner with reliable measures of the model's actual degree of commitment to (or belief in) the representations that he has inexpensively expressed symbolically (e.g., verbally). Learners should use such displays in determining how much to commit to a particular culturally acquired mental representation such as an ideology, value, belief or preference. After laying this out, I summarize supporting findings from psychology.
Building on this, Part II explores whether such a learning bias could create interlocking sets of beliefs and costly practices that are self-stabilizing. That is, can this adaptive learning bias lead to the emergence of stable combinations of beliefs and costly practices (displays) in a social group that could not otherwise persist (remain stable)? My formal model reveals the wide-ranging conditions under which costly practices (acting as CREDs) and associated beliefs are self-stabilizing. Such stable cultural evolutionary states are interesting because they show how particular displays or acts, which appear costly to one who does not hold the relevant corresponding belief, can be sustained by cultural evolution.
Part III considers the possibility that such an interlocking system could also sustain costly practices that elevate the commitment of group members to beliefs that promote group benefits, larger-scale cooperation and solidarity, and — in particular — favor success in competition with other social groups (or institutions). This competition among stable culturally-evolved states favors social groups that are increasingly constituted by combinations of (a) beliefs that favor in-group cooperation/harmony and out-group competition, and (b) practices (e.g. rituals) that maximize participants' commitment to those beliefs.
To assess the plausibility of this account and compare it with existing approaches based on signaling, I summarize evidence indicating that (1) belief-practice (ritual) combinations are spread by cultural group selection (CGS); (2) participation in costly rituals is associated with prosocial in-group behavior, because costly rituals transmit commitment to group-beneficial beliefs/goals to participants; and (3) institutions requiring costly displays are favored by cultural evolution because costly displays by members transmit higher levels of belief commitment and thereby promote cooperation and success in intergroup or interinstitution competition.
Together these three parts lay out a process, initiated by an evolved learning bias, that connects costly, even extravagant, displays to cooperation and commitment to a group's beliefs and ideology. The more costly the displays are, the potentially deeper the degree of transmitted commitment.
I close by discussing how such processes may illuminate a number of puzzling aspects of religion, including why (1) religions are often associated with prestigious paragons of virtue who make (or made) costly sacrifices; (2) martyrdom is so persuasive; (3) religions and rituals are loaded with sacrifices of various kinds; (4) gods and ancestors want costly acts; and (5) religious leaders often take costly vows, such as those involving poverty and celibacy.
Section snippets
The evolution of our cultural capacities
The application of the logic of natural selection to the evolution of social learning has produced an array of novel theoretical insights, hypotheses and empirical findings (for reviews, see Henrich and McElreath, 2006, Richerson and Boyd, 2005). One central line of inquiry arising from this research program has focused on how selection has shaped our cultural learning processes in order to more effectively acquire ideas, beliefs, values, preferences and practices from others in our social
Part I: The emergence of an adaptive challenge
The evolution of high-fidelity cultural learning, with all its adaptive benefits, increases the potential for exploitation by other members of one's group because cultural learners are open to modifying their behavior, and underlying mental representations, in response to others'. Models can manipulate learners by misrepresenting their (the model's) true underlying representations or commitments. Tom Sawyer famously did this when he manipulated his mates into believing that he (and they)
Part II: How do CREDs affect cultural evolution?
If indeed our species is endowed with a CRED bias in cultural learning, what implications does this have for cultural evolution? How might this influence the kinds of stable cultural phenomena we observe across societies? Could it explain the widespread and unusual nature of costly displays such as animal sacrifice, subincision, scarification, self-mutilation or tattooing?
Building on standard cultural evolutionary approaches, this model adds a cognitive mechanism that weighs CREDs to the usual
Part III: Cultural group selection favors interlocked belief–display combinations that increase cooperation
Part II demonstrated that a genetically evolved reliance on CREDs can, under a wide range of conditions, yield a cultural evolutionary process with multiple stable equilibria. If this were all there were to it, the story would not be very interesting as individuals at equilibria involving costly acts would get lower payoffs than those in groups stabilized at the other equilibrium. However, showing that a reliance on CREDs can stabilize costly practices, opens the door to the possibility that
Discussion: implications for understanding religion
These ideas have numerous implications for understanding the cultural evolution of various religious phenomena. Here I will sketch how some of these processes may have shaped certain aspects of religion.
Conclusion
I began by hypothesizing that, over the course of human evolution, cultural learners faced an adaptive challenge created by our increasing capacities for symbolic (cheap) cultural transmission. To meet this challenge natural selection favored a reliance on CREDs in determining how much to commit to, or believe in, a particular representation. Learners evolved to look for displays (often actions) that indicate a model's degree of commitment to, or belief in, verbally expressed representations.
Acknowledgments
Bob McCauley, Harvey Whitehouse, Justin Barrett, Robert Boyd, Ara Norenzayan, Jon Lanman, Natalie Henrich, and Richard McElreath provided helpful comments and critiques. Thank you.
References (90)
Is the repeated prisoner's dilemma a good model of reciprocal altruism?
Ethology and Sociobiology
(1988)- et al.
Punishment allows the evolution of cooperation (or anything else) in sizable groups
Ethology & Sociobiology
(1992) - et al.
Group beneficial norms can spread rapidly in a structured population
Journal of Theoretical Biology
(2002) - et al.
Group selection among alternative evolutionarily stable strategies
Journal of Theoretical Biology
(1990) - et al.
Voting with your feet: Payoff biased migration and the evolution of group beneficial behavior
Journal of Theoretical Biology
(2009) - et al.
Cognitive templates for religious concepts: cross-cultural evidence for recall of counter-intuitive representations
Cognitive Science
(2001) - et al.
The effect of adults' eating on young children's acceptance of unfamiliar foods
Journal of Experimental Child Psychology
(1975) Cultural group selection, coevolutionary processes and large-scale cooperation
Journal of Economic Behavior & Organization
(2004)- et al.
Why people punish defectors: Weak conformist transmission can stabilize costly enforcement of norms in cooperative dilemmas
Journal of Theoretical Biology
(2001) - et al.
The Evolution of prestige: Freely conferred deference as a mechanism for enhancing the benefits of cultural transmission
Evolution and Human Behavior
(2001)