Extension #1: Religion is primarily a method for defining a tribe: Those folks who are on the same team. It seems to have all the benefits that one can get from a good tribal system, and most of the costs. Indeed, as far as I can tell, it is nearly the only method for defining a tribe in the modern world.
Mutual aid society
Pre-immigration nation-states tend to be good for tribalism too...though the larger they get the weaker they get in terms of shared identity and mutual (voluntary) aid.
Moldbug's Cathedral (near-socialist, environmentalist, academic, semi-meritocratic, democratic fundamentalist, mostly non-science/engineering types) also functions moderately well as a tribe...but they have been working very hard to conceal the existence of the tribe. If it is identified clearly as a tribe, it fails.
I was inspired to write the post by Roderick Long's discussion of the most recent Objectivist Schism. Clearly a result of the conflict between a tribal identity and truth-pursuits.
"David Hume" at SecularRight posts another discussion that prodded my thinking.