Review by Lawrence A. Whitney, 2008
Sosis, Richard. 2003. “Why aren’t we all Hutterites? Costly signaling theory and religious behavior.” Human Nature 14: 91-127.
Sosis, Richard. 2004. “The adaptive value of religious ritual.” American Scientist 92: 166-172.
Sosis, Richard; Candace Alcorta. 2003. “Signaling, solidarity and the sacred: The evolution of religious behavior.” Evolutionary Anthropology 12: 264-274.
Sosis, Richard; Bradley Ruffle. 2003. “Religious ritual and cooperation: Testing for a relationship on Israeli religious and secular Kibbutzim.” Current Anthropology 44: 713-722.
Sosis, Richard; Bradley Ruffle. 2004. “Ideology, religion, and the evolution of cooperation: Field experiments on Israeli Kibbutzim.” Research in Economic Anthropology 23: 87-115.
In these five articles, Richard Sosis and colleagues apply costly signaling theory from the field of evolutionary psychology to religious behaviors in order to understand the evolutionary advantages of religions. Costly signaling theory (CST) begins by noting the need for mutual trust in order for humans to cooperate. Cooperation is evolutionarily advantageous, but cooperating with people who are untrustworthy is disadvantageous. Thus, being able to discern who to trust, and therefore with whom to cooperate, is important. Committed members of groups are more trustworthy than less committed or uncommitted members. One way to measure commitment is a person’s willingness to participate in costly behavior, such as unconventional styles of dress. Costly behaviors then function as signals to other members of the group that the person is committed and therefore trustworthy and suitable for cooperation.
Sosis empirically tests CST with religious, socialist and privatized kibbutzim. The theory is confirmed first in that the privatized kibbutzim show no more cooperation than among regular city residents while socialist kibbutzim show more cooperation and the most religious, and therefore most highly committed, show the highest levels of cooperation. Sosis goes on to argue that religious ideologies engender greater commitment than costly but secular ideologies because they are unverifiable in their ultimacy and so rely upon seemingly more stable (convincing) religious experiences. The necessity of religious experiences being unfalsifiable in order for religious groups to bring about the levels of cooperation they engender is important for students of religious experience. On the one hand, attempts to make religious experience subject to falsification could reduce levels of cooperation in religious groups and thus lessen the evolutionary advantages of religion, potentially contributing to secularization. On the other hand, making religious experiences subject to verification makes them more subject to correction internally, and thus reducing potential abuse in religious groups, and available for intergroup dialogue and comparison, and thus reducing intergroup hostility and violence. Sosis notes that cooperation is fundamentally an intragroup benefit precisely by increasing a group’s ability to defend against and compete with other groups. Religion, then, has likely always been a significant contributor to intergroup violence by creating conditions for the highest levels of cooperation.