But the idea that we can simply argue away religion has little factual support. Although a recent study by psychologists Will Gervais and Ara Norenzayan indicates that people are less prone to think religiously when they think analytically, other studies suggest that seemingly contrary evidence rarely undermines religious belief, especially among groups welded by ritualized sacrifice in the face of outside threats. Norenzayan and others also find that belief in gods and miracles intensifies when people are primed with awareness of death or when facing danger, as in wartime.
Moreover, the chief complaint against religion -- that it is history's prime instigator of intergroup conflict -- does not withstand scrutiny. Religious issues motivate only a small minority of recorded wars. The Encyclopedia of Wars surveyed 1,763 violent conflicts across history; only 123 (7 percent) were religious. A BBC-sponsored "God and War" audit, which evaluated major conflicts over 3,500 years and rated them on a 0-to-5 scale for religious motivation (Punic Wars = 0, Crusades = 5), found that more than 60 percent had no religious motivation. Less than 7 percent earned a rating greater than 3. There was little religious motivation for the internecine Russian and Chinese conflicts or the world wars responsible for history's most lethal century of international bloodshed.
Indeed, inclusive concepts such as "humanity" arguably emerged with the rise of universal religions. Sociologist Rodney Stark reveals that early Christianity became the Roman Empire's majority religion not through conquest, but through a social process grounded in trust. Repeated acts of altruism, such as caring for non-Christians during epidemics, facilitated the expansion of social networks that were invested in the religion. Likewise, studies by behavioral economist Joseph Henrich and colleagues on contemporary foragers, farmers, and herders show that professing a world religion is correlated with greater fairness toward passing strangers. This research helps explain what's going on in sub-Saharan Africa, where Islam is spreading rapidly. In Rwanda, for example, people began converting to Islam in droves after Muslims systematically risked their lives to protect Christians and animists from genocide when few others cared.
Although surprisingly few wars are started by religions, once they start, religion -- and the values it imposes -- can play a critical role. When competing interests are framed in terms of religious and sacred values, conflict may persist for decades, even centuries. Disputes over otherwise mundane phenomena then become existential struggles, as when land becomes "Holy Land." Secular issues become sacralized and nonnegotiable, regardless of material rewards or punishments. In a multiyear study, our research group found that Palestinian adolescents who perceived strong threats to their communities and were highly involved in religious ritual were most likely to see political issues, like the right of refugees to return to homes in Israel, as absolute moral imperatives. These individuals were thus opposed to compromise, regardless of the costs. It turns out there may be a neurological component to such behavior: Our work with Gregory Berns and his neuroeconomics team suggests that such values are processed in the brain as duties rather than utilitarian calculations; neuroimaging reveals that violations of sacred values trigger emotional responses consistent with sentiments of moral outrage.
Historical and experimental studies suggest that the more antagonistic a group's neighborhood, the more tightly that group will cling to its sacred values and rituals. The result is enhanced solidarity, but also increased potential for conflict toward other groups. Investigation of 60 small-scale societies reveals that groups that experience the highest rates of conflict (warfare) endure the costliest rites (genital mutilation, scarification, etc.). Likewise, research in India, Mexico, Britain, Russia, and Indonesia indicates that greater participation in religious ritual in large-scale societies is associated with greater parochial altruism -- that is, willingness to sacrifice for one's own group, such as Muslims or Christians, but not for outsiders -- and, in relevant contexts, support for suicide attacks. This dynamic is behind the paradoxical reality that the world finds itself in today: Modern global multiculturalism is increasingly challenged by fundamentalist movements aimed at reviving group loyalty through greater ritual commitments to ideological purity.
So why does it matter that we have moved past the -isms and into an era of greater religiosity? In an age where religious and sacred causes are resurgent, there is urgent need for scientific effort to understand them. Now that humankind has acquired through science the power to destroy itself with nuclear weapons, we cannot afford to let science ignore religion and the sacred, or let scientists simply try to reason them away. Policymakers should leverage scientific understanding of what makes religion so potent a force for both cooperation and conflict, to help increase the one and lessen the other.