Its hardly a new idea. One problem is that there is a lot more to religion than ethics. It also assumes that religious rules of behaviour are global optimums. It fails to explain why religions spread too - why would people believe in the religion that promotes cooperation, rather than one another one? In fact, I would argue, that, in the west, far more people are moralistic therapeutic deists than Christians.

There is also a lack of evidence it works. I do not think Christians are consistently greatly more socially cooperative than atheists. Maybe more inclined to help people on the fringes of society - e.g. running food banks here in the UK, very active in poverty charities globally but while good, I cannot believe it has a sufficient consistent effect to provide an advantage to a society that follows it.

Fear of hell as a motivator is limited to some Christian denominations but is not often mentioned by other denominations (I am mostly familiar with Catholic and Anglican churches) or in the Bible, or Christian writings, or in sermons or in religious discussions. Christian universalists and others do not believe in any form of hell at all!

It might work with a religion once established (religious societies do better because of that cooperation) but it does not explain how religions spread in the first place. Its a lot more likely to apply to a religion that has been long established in a relatively stable setting so it is credible as an explanation of much of ancient Jewish law that seems strange to us now (e.g. what to eat, not plucking fruit from young trees etc) that often seems off from a modern perspective.

The comic isn't saying this is the main point of religions, it's only saying it's one thing that happens within religions. For example, religious communities have their own social norms that are fundamental to the religion, and allow for coordinated actions you don't see elsewhere, like an Amish barn raising.

I take a Jungian view that a major useful thing religions offer is a framework for relating to the unconscious. One key part of that is to have a clear sense of ethics, and to align ones actions with it, which is generally good for your mental health.

> so it is credible as an explanation of much of ancient Jewish law that seems strange to us now (e.g. what to eat, not plucking fruit from young trees etc) that often seems off from a modern perspective.

One example theory I remember reading at some point was the prohibition against eating shellfish: In the area the religion arose, it would have most likely gone bad by the time it was brought that far inland.

That seems like a very forced theory. By the time shellfish is bad enough to present a health risk, it smells, looks, and feels repugnant, one doesn't need a religious system to know not to eat it.

Shellfish are susceptible to harmful algal blooms like red tide, that can make them very dangerous.

Coastal foraging cultures that don't have bans on eating shellfish, instead have complex knowledge about when, where, and how to prepare and eat them. It's the same with mushrooms- cultures either universally ban them, or deeply educate everyone about them. All cultures globally with access to these foods have a system here- it's not unique to Judaism.