Psychological study: Punishing gods enhance social coherence.

http://www.nature.com/nature/journal/vaop/ncurrent/full/nature16980.html
http://www.nature.com/nature/journal/vaop/ncurrent/pdf/nature16980.pdf

Abstract:
Here we focus on one key hypothesis: cognitive representations of gods as increasingly knowledgeable and punitive, and who sanction violators of interpersonal social norms, foster and sustain the expansion of cooperation, trust and fairness towards co-religionist strangers.

...

Holding a range of relevant variables constant, the higher participants rated their moralistic gods as punitive and knowledgeable about human thoughts and actions, the more coins they allocated to geographically distant co-religionist strangers relative to both themselves and local co-religionists. Our results support the hypothesis that beliefs in moralistic, punitive and knowing gods increase impartial behaviour towards distant co-religionists, and therefore can contribute to the expansion of prosociality.



Text:
To account for the emergence of these patterns, some evolutionary approaches to religion have theorized that cultural evolution may have harnessed and exploited aspects of our evolved psychology, such as mentalizing abilities, dualistic tendencies and sensitivity to norm compliance, to gradually assemble configurations of supernatural beliefs that promote greater cooperation and trust within expanding groups, leading to greater success in intergroup competition. Of course, given that cultural evolution can produce self-reinforcing stable patterns of beliefs and practices, these supernatural agent concepts may also have been individually favoured within groups due to mechanisms related to signalling, reputation and punishment.

...

At the societal level, several lines of converging evidence are consistent with this hypothesis. For example, after controlling for key correlates, analyses of cross-cultural data sets show that larger and more politically complex societies tend to have more supernatural punishment and moralistic deities...





---------

For a long time, it's been my opinion that belief and religion aren't phenomena unto themselves but side-effects of evolutionary adaptions to life in societies.

My hypothesis is that the psychological tendency to "believe" stems from an advantageous neurological evolutionary trait: People who believe learn faster, and thus are more likely to survive, than people who doubt and test.
Populations solely consisting of believers would stagnate. And populations solely consisting of doubters would be socially unstable and have a high mortality-rate. It takes both: Doubters for abstract progress and believers for tangible day-to-day business. That's why neither of these fundamentally different conditions has been able to fully take over evolutionarily.
It gets interesting when you change the parameters of survival that determine evolution: In an environment where technological progress becomes irrelevant, the "stability" of believers would give them an evolutionary advantage. In an environment where experiments are no longer real-life risks to you and your society, the faster rate of technological progress of doubters would give them an evolutionary advantage. (For example: You have a new idea how to tend a crop-field. Can you afford to divert the necessary time and manpower into developing this idea? Or would diverting this time and manpower from food-production put you and your society at risk?)

And now this paper shows that religion increases social stability within societies with one mutually shared religion.