Original Article
The evolution of costly displays, cooperation and religion: credibility enhancing displays and their implications for cultural evolution

https://doi.org/10.1016/j.evolhumbehav.2009.03.005Get rights and content

Abstract

This paper lays out an evolutionary theory for the cognitive foundations and cultural emergence of the extravagant displays (e.g., ritual mutilation, animal sacrifice and martyrdom) that have so tantalized social scientists, as well as more mundane actions that influence cultural learning and historical processes. In Part I, I use the logic of natural selection to build a theory for how and why seemingly costly displays influence the cognitive processes associated with cultural learning — why do “actions speak louder than words?” The core idea is that cultural learners can both avoid being manipulated by their models (those they are inclined to learn from) and more accurately assess their belief commitment by attending to displays or actions by the model that would seem costly to the model if he held beliefs different from those he expresses verbally. Part II examines the implications for cultural evolution of this learning bias in a simple evolutionary model. The model reveals the conditions under which this evolved bias can create stable sets of interlocking beliefs and practices, including quite costly practices. Part III explores how cultural evolution, driven by competition among groups or institutions stabilized at alternative sets of these interlocking belief-practice combinations, has led to the association of costly acts, often in the form of rituals, with deeper commitments to group beneficial ideologies, higher levels of cooperation within groups, and greater success in competition with other groups or institutions. I close by discussing the broader implications of these ideas for understanding various aspects of religious phenomena.

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)

  • SalvyS.-J. et al.

    Peer influence on pre-adolescent girls' snack intake: Effects of weight status

    Appetite

    (2007)
  • SosisR. et al.

    Scars for war: evaluating alternative signaling explanations for cross-cultural variance in ritual costs

    Evolution and Human Behavior

    (2007)
  • SpencerC. et al.

    Multilevel selection and political evolution in the Valley of Oaxaca

    Journal of Anthropological Archaeology

    (2001)
  • WalsterE. et al.

    On increasing the persuasiveness of a low prestige communicator

    Journal of Experimental Social Psychology

    (1966)
  • AtranS.

    In Gods We Trust: The Evolutionary Landscape of Religion

    (2002)
  • AtranS.

    Genesis of suicide terrorism

    Science

    (2003)
  • AtranS. et al.

    Folkecology, cultural epidemiology, and the spirit of the commons — A garden experiment in the Maya Lowlands, 1991–2001

    Current Anthropology

    (2002)
  • AtranS. et al.

    Religion's evolutionary landscape: Counterintuition, commitment, compassion, communion

    Behavioral and Brain Sciences

    (2004)
  • Barrett, H. C. (2007). Evolved developmental systems and prepared learning about dangerous animals in children....
  • BarrettJ.L. et al.

    Spreading nonnatural concepts

    Journal of Cognition and Culture

    (2001)
  • BergstromB. et al.

    Extending the testimony problem: Evaluating the truth, scope, and source of cultural information

    Child Development

    (2006)
  • BergstromC.T. et al.

    Separating equilibria in continuous signalling games

    Philosophical Transactions of the Royal Society of London Series B-Biological Sciences

    (2002)
  • BettingerR.L. et al.

    The Numic Spread: Great Basin cultures in competition

    American Antiquity

    (1982)
  • BirchL.L.

    Effects of peer model's food choices on eating behaviors on preschooler's food preferences

    Child Development

    (1980)
  • BirchL.L.

    Children's food preferences: developmental patterns and environmental influence

    Annals of Child Development

    (1987)
  • BoydD.

    Life without pigs: Recent subsistence changes among the Irakia Awa, Papua New Guinea

    Human Ecology

    (2001)
  • BoydR. et al.

    Culture and the Evolutionary Process

    (1985)
  • BoyerP.

    Religion Explained: The Evolutionary Origins of Religious Thought

    (2001)
  • BoyerP. et al.

    Precaution systems and ritualized behavior

    Behavioral and Brain Sciences

    (2006)
  • BryanJ.H.

    Model affect and children's imitative altruism

    Child Development

    (1971)
  • BryanJ.H. et al.

    Words and deeds about altruism and the subsequent reinforcement power of the model

    Child Development

    (1971)
  • BryanJ.H. et al.

    The impact of words and deeds concerning altruism upon children

    Child Development

    (1970)
  • BryanJ.H. et al.

    Preaching and practicing generosity: Children's actions and reactions

    Child Development

    (1970)
  • CronkL.

    Evolutionary theories of morality and the manipulative use of signals

    Zygon

    (1994)
  • DunckerK.

    Experimental modification of children's food preferences through social suggestion

    Journal of Abnormal Psychology

    (1938)
  • DurkheimE.

    Elementary Forms of Religious Life

    (1995)
  • EaglyA.H. et al.

    Causal inferences about communicators and their effect on opinion change

    Journal of Personality and Social Psychology

    (1978)
  • EdgertonR.B.

    Sick Societies: Challenging the Myth of Primitive Harmony

    (1992)
  • ElliotR. et al.

    The modeling of sharing: Effects associated with vicarious reinforcement, symbolization, age, and generalization

    Journal of Experimental Child Psychology

    (1970)
  • FehrE. et al.

    The nature of human altruism

    Nature

    (2003)
  • FesslerD.M.T.

    Meat is good to taboo: Dietary proscriptions as a product of the interaction of psychological mechanisms and social processes

    Journal of Cognition and Culture

    (2003)
  • FlanneryK.V. et al.

    Formative Mexican chiefdoms and the myth of the ‘Mother Culture’

    Journal of Anthropological Archaeology

    (2000)
  • FredricksonB.L.

    What good are positive emotions

    Review of General Psychology

    (1998)
  • Gil-WhiteF.

    Are ethnic groups biological ‘species’ to the human brain? Essentialism in our cognition of some social categories

    Current Anthropology

    (2001)
  • Ginges, J., Hansen, I., & Norenzayan, A. (2007). Religion and support for suicide attacks. Unpublished...
  • Cited by (0)

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