It seems very likely to me that tribal groups in prehistory observed that "eating some things leads to illness and sometimes death; eating other things seems to lead to health or happiness or greater utility" and some very clever group of people starting compiling a system of eating rules that seemed to work. It became traditional to hand over rules for eating, and other activities, to their children. Rules like "If a garment has a visible spot of mildew, either cut out the mildewed spot with a specified margin around it or discard it entirely, for god's sake don't store it with your other garments" or "don't eat insects that you don't specifically recognize as safe and nutritious" or 'don't eat with unclean hands, for a certain technical definition of 'unclean', for example, don't touch a rotting corpse then stuff your face or deliver a baby with those hands" etc. etc.

Then much much later, some of the descendants of some of those tribes thought to write a bunch of this stuff down before it could be forgotten. They ascribed the origin of the rules to a character representing "The best collective wisdom we have available to us" and used about ten different names for that character, who was seen as a collection of information much like any person is, but the oldest and wisest known collection of information around.

Then when different branches of humanity ran into each other and found out that other branches had different rule sets, different authority figures, and different names for the same thing as well as differing meanings for the same names in many cases, hilarity ensued.

Then a group of very very serious atheists came and said "We have the real truth, and our collective wisdom is much much better than that of the ancient people who actually fought through fire and blood, death and disease and a shitstorm of suffering to hand us a lot of their distilled wisdom on a platter, so we could then take the cream of what they offered, throw away the rest, and make fun of their stupid superstitions while not acknowledging that they actually did extremely well for the conditions they experienced"

Religious minds did most of the heavy lifting to get rationality at least as far as Leibniz and Newton, both of whom were notably religious. I'm not saying that the religious mindset is correct or superior, but the development of rational thought among humans has been like a relay race carrying a torch for a million years, and then when the torch is at the finish line (when it gets passed on to nonhumans) a subset of the people who carried the torch for the last little bit doesn't need to say "Hah we are so much better than the people who fought and died under the banner of beliefs at variance with our own". This is a promulgation of what is /bad/ about religion, and I see a lot of it in this group. I love the group but would really like it even better if people showed a tiny bit of respect for the minds that fought through the eras of slavery and religious war and other evils, instead of proclaiming very loudly about how wonderful they are compared to everyone else.

I mean, you ARE wonderful, you are doing amazing things, but... come on.

Not that I am any better, here I am bashing you lovely people because your customs are at variance with my own - but that's what reading this group has taught me to do!

(I'm neither a theology scholar nor an anthropologist, so I may lack some important background on this.)

I agree that the idea of early church leaders isolating members in order to explicitly limit the introduction of new ideas sounds far-fetched. It strikes me as the kind of thing that would only be said after the fact, by a historian looking for meaning in the details. But attributing those member-isolating rules to something like "preserving group identity" seems like the same thing.

I find myself wondering if something like the anthropic principle is at work here, i.e. the only religious groups to survive that long are the ones who historically isolated their members from outside ideas. There's probably a more general term for what I'm getting at.