It means that it is ADAPTIVE.
I realize that it is currently very trendy to be opposed to "tribalism."
Don't know about "trendy". It's just that in an increasingly globalizing and multi-cultural world, tribalism is the main psychological cause of wars. Us vs Them.
And even within single cultures. It's what makes the fans of one football club break the face of the supporters of another football club.
I will also add, btw, that evolution more then likely did NOT "select for" religious people.
Religion more then likely is merely a byproduct, a side effect, of
other psychological constructs.
Primarily the tendency to engage in type 2 cognition errors (the false positive) and the assumption of agency in otherwise random events as a survival mechanism, which forms the basis for superstition.
The classic example is hearing a noise in the bushes. Is it just the wind, or is it a dangerous predator sneaking up on you for his lunch?
Those individuals that assume the dangerous predator will run. Those that don't will stay put. If it turns out to be a predator, those that didn't run will die.
If you run and it's not a predator, you just engaged in a type 2 cognition error and infused agency in a mere sound.
Natural selection favors those more likely to engage in that cognition error. If you run and it was just the wind, you didn't lose anything. You just went for a jog / sprint. The vast majority of animals that are seen as a meal by other animals, tend to engage in exactly such behavior.
A crockodile for example, will not be jumping up / running away when it hears a sound in the bushes. But rabbits, squirels, birds, etc will.
The propensity to invent and hold religious beliefs, is thus most likely a byproduct of that survival mechanism.
Just thought I'ld point that out.
Anyway...................