There is a vast literature on the origins, functions, and proliferation of religious cognition, and an equal amount of debate among its researchers. Although no uniformly agreed-upon theory of the evolution of religion currently exists, there are particular hypotheses that have gained traction. One generally undisputed benefit of religion’s adaptive functionality, which helped drive the spread of uniform supernatural beliefs via cultural transmission, is ingroup cooperation. By way of ingroup/outgroup psychology, any mechanism that enhances ingroup cohesion will almost indefinitely also increase outgroup aggression (Teehan, 2010). Unfortunately, religion is no exception and thus is also the basis for much intergroup conflict.
Religion & Cooperation
Several researchers have posited that a primary function of religion is to promote intragroup cooperation, whereby constituents employ rituals and devotion as a way of signaling commitment to the group (Iannaccone, 1992). In addition to signaling commitment to foster group coordination, religions bind individuals into moral communities (Graham & Haidt, 2010) especially by instilling a fear of punishment by supernatural agents, which increases the probability of self-control, prosocial behavior, and real-world detection and punishment for selfish actions or violations of social norms (Johnson, 2009).
In experimental studies, priming religious concepts increased prosocial behavior, fostering greater cooperation and generosity even between strangers, and in some cases regardless of religious affiliation (Shariff & Norenzayan, 2007; Bremner et al., 2011). Priming religiosity also increased submissive behaviors and attitudes (Saroglou et al., 2009), contributing to the psychology of social cooperation. Rounding et al. (2012) found that subjects primed with religious themes exercised greater self-control, which regulates prosocial behavior.
Groups that function in greater uniformity, with significant cooperative and altruistic investments toward in-group members and away from out-group members, will outcompete groups that are less cooperative (Henrich, 2004). If highly cooperative and coordinated groups outcompete less organized groups, and religion is a strong facilitator of such coordination, then shared supernatural beliefs and displays of commitment to those beliefs should prove to be culturally and thus biologically adaptive. Hence, the evolution of religious systems.
Religion & Conflict
Teehan (2010) suggests that some form of intergroup conflict is always present in religion since the psychological elements that motivate pro-community moral attitudes are the same that produce out-group prejudice and aggression. For instance, Johnson et al. (2010) found that subjects “subliminally primed with Christian words displayed more covert racial prejudice against African-Americans (Study 1) and more general negative affect toward African-Americans (Study 2) than did persons primed with neutral words” (p.119). Further, the stronger a religious person identifies with his in-group, the more likely he is to have aggressive attitudes toward the out-group, including cognitively dehumanizing out-group members (Struch & Schwartz, 1989).
However, beyond simply a by-product of in-group bias—which often engenders an automatic out-group prejudice—religious support of aggression toward out-groups may have taken on a life of its own in its adaptive significance. In other words, aggression itself may be an important evolutionary reason for the spread of supernatural beliefs, separate from its by-product role in fostering highly-coordinated groups. Kurzban & Christner (2011), MacNeill (2004), and Johnson & Reeve (2013) suggest that religion may have been an adaptation not simply for the broad notion of group cooperation, but more particularly for coordination during intergroup violence. For instance, Johnson and Reeve (2013) suggest that for the purposes of warfare, religion increases ingroup cooperation, confidence, comradeship, righteousness, justified cause, dehumanization of the enemy, heroism and self-sacrifice, and the supplanting of material costs with supernatural rewards.
This notion that aggression is an explanation for religion is often overlooked due to the various prosocial and charitable aspects of contemporary religious values; however, in several experiments where religious psychology has been shown to increase prosocial attitudes, it has done so primarily with regard to other ingroup members, while promoting antisocial sentiments toward outgroups (Preston & Ritter, 2013; Saroglou et al, 2005). Further, there is an abundance of current and historical examples of religion being used to promote and justify violence against out-group members and against in-group violators of cultural norms, from larger-scale industrialized crusades to small-scale tribal raids (McConochie, 2010; Juergensmeyer, 2003). In a survey of six religions in six nations, attendance at religious services—a marker of group allegiance—was positively correlated with support for suicide attacks, willing martyrdom, and out-group hostility, while prayer to God—an index of religious devotion—was not (Ginges et al., 2009). Bushman et al. (2007) found that aggression increased in college students after reading a violent passage that was purportedly from the Bible or when the passage mentioned God compared with reading a violent passage without any religious context. Topalli et al. (2012) found that criminals use the absolvitory tenets of religion to justify, rationalize and even encourage offending. Ideas of an authoritarian God (Johnson et al, 2013), ideas of an afterlife (Sosis, Phillips & Alcorta, 2011), and scriptural violence (Bushman et al, 2007) have all been shown to increase aggression.
Throughout history, humans have used the idea of God being on their side to war with other sides, even when their opponents were much larger or stronger. This strategy has led to success across a variety of religious cultures, including some of today’s most prominent religions, which originally spread via small crusades against more dominant cultures (Montgomery, 1991). In fact, religion has been shown to increase the chance of intergroup conflict (Seul, 1999), to impact modern armed conflict (Basedau et al, 2011), to assist in military discipline (Fisher, 1971) and military leadership (Fry et al, 2005), to motivate soldiers to participate in warfare (Ben-Dor & Pedahzur, 2006) and to mitigate existential fear during combat (Wansink & Wansink, 2103).
A single socio-cognitive program that simultaneously implements historical justifications and narratives reinforcing conflict, activates the psychological states required to participate in warfare, and employs the notion of a powerful, omniscient ally or system that supports the group, punishes non-participants, and guarantees eternal rewards for participants no human-developed social system can promise (Johnson & Reeve, 2013), may top the list of powerful enough mechanisms to motivate intense personal risk for the good of the group. Such a program would make for a powerful mental heuristic for participation in intergroup conflict, and thus presumably be adaptive for the purposes of helping group members engage and perhaps even become more successful in intergroup violence. Those groups that coordinate and perform well in violent conflict will outlast those that do not, and therefore survive to pass on the very traits and cultural systems that helped them do so. Hence, the evolution of religion has likely conferred group-level benefits for both intragroup cooperation and intergroup conflict.
The question remains: Is it possible for religion, in its current form, to help resolve intergroup conflicts, rather than exacerbate them by activating an ingroup-outgroup bias? With the rampant advocating of violence in the name of God, both historically and in modern times, the link between group-level conflicts and religion must be better understood. Future research in the area may present important contributions to the international discussion on socio-religious peacekeeping efforts among conflict management professionals, politicians, and religious leaders.
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