First off, let me clear the field of an obvious source of what I think is rather fruitless discussion. The authors begin by summarizing three models of the evolution of religion: the evolutionary group selection scenario (religion as an adaptation for group living), the cultural by-product scenario (religion derives from the necessity of a theory of others’ mind and sensitivity to one’s reputation), and the cultural group selection scenario (where competition among social groups favors the spread of costly practices to maintain in-group cohesion). I have said repeatedly that we simply do not have the empirical data to seriously test genetic-evolutionary explanations for most human behaviors, so I am completely neutral about alternative scenarios that deal with that aspect of the problem. Moreover, following Jablonka and Lamb (2005), I count cultural inheritance as a legitimate form of evolutionarily relevant inheritance. This means that any of the above scenarios (or a combination thereof) may have occurred without major involvement of genes, by direct transmission of cultural practices.
Ok, that being out of the way, let’s take a look at what Norenzayan and Shariff say. To begin with, they debunk the oft-repeated claim that religiosity increases charitability. It turns out studies that have made that link are entirely based on self-reporting, a notoriously unreliable source of behavioral evidence. When one looks into experimental studies of the issue, the picture changes dramatically. A series of “Good Samaritan” studies found that people’s actual (as opposed to self-reported) charitable behavior shows no correspondence whatsoever with the degree of religious belief. Secular people are just as likely (or not) to help someone in distress as are religious people. Interestingly, however, researchers have been able to show that a strong link between religiosity and prosocial behavior does emerge, but only when there is a self-reputation enhancing egoistic motivation: religious people are more likely to engage in prosocial behavior if they know that there is a good chance that their reputation in the group will be positively affected.
Perhaps one of the most interesting sets of experiments reported by Norenzayan and Shariff concerns what happens when people are reminded of a morally watchful authority -- religious or secular. In a control group that was not “primed” with a god-like concept, people behaved selfishly (most pocketed an available sum of money without sharing). When participants were primed with a god reminder, however, the modal behavior switched to fairness (they split the money). So, does religion trigger altruistic behavior after all? Nope. Here’s the kicker: people that were primed with reminders of a secular moral authority were just as altruistic as the religiously primed ones! It isn’t religion, it is the presence of a moral authority that does the trick.
Another spectacular finding deals with the effect of religiosity on group survival. Researchers have mined historical information on hundreds of communes that were started in the United States during the 19th century, some religious, some secular (mostly of socialist inspiration). Once again, a prima facie interpretation of the data would seem to give credence to the idea that religion is good for sociality: at any given point in time, religious communes were four times as likely to survive to the following year as their secular counterparts. However, more in-depth analyses revealed that one needs to be weary before jumping to conclusions: it turns out that the real predictor of commune longevity was not religiosity, but the number of costly requirements for membership! The more costly it is to belong, the more likely members are to stick with it (that’s also why it’s better to subscribe to an expensive gym if you really want to motivate yourself…). The overall difference between religious and non-religious communes was simply due to the fact that the latter, on average, imposed much less costly requirements. (Note that “requirements” here does not just mean monetary ones, but also engaging in rituals, church attendance, constrained sexual practices, and so on. Still, perhaps atheist organizations should start asking their membership for a sizable percentage of their income, just as many fundamentalist denominations do.)
Finally, Norenzayan and Shariff looked into another interesting prediction that people have made about the relationship between religion and prosociality. According to standard theory, the two original sources of moral behavior are kin selection (you help your relatives because they carry some of your genes) and reciprocal altruism (where there is an expectation of favors being returned). The problem is that these two mechanisms begin to break down for groups that are much larger than about 150 individuals (all that our neocortex can keep track of). What then? The hypothesis here is that gods kick in as a supplementary and increasingly important moral lever. If so, then there should be a positive relationship between the size of a society and the moralizing of their gods. Sure enough, researchers found that although most societies do not, in fact, worship gods that dictate morality, all large groups switch to moral-dictating deities. Does that mean that religion is, after all, necessary for the stability of human groups? Again, no, because modern secular social contract-enforcing institutions (police, courts, etc.) efficiently replace the original function of “big gods,” as plainly demonstrated by the case of most western societies, which are both highly secular and stable.
Norenzayan and Shariff end with one further cautionary statement to people who insist that religion must be good for society, and a direct quote here is best: “Religious prosociality is not extended indiscriminately; the ‘dark side’ of within-group cooperation is between-group competition and conflict.” In this age of holy wars and cross-cultural clashes, it is indeed hard to underestimate the destructive power of religion.
Ara Norenzayan and Azim F. Shariff,'The Origin and Evolution of Religious Prosociality', Science 3 October 2008: Vol. 322. no. 5898, pp. 58 - 62 DOI: 10.1126/science.1158757 Jablonka, E. and M. J. Lamb (2005). Evolution in Four Dimensions: Genetic, Epigenetic, Behavioral, and Symbolic Variation in the History of Life. Cambridge, MA, MIT Press.