What is the function of religion?

[Anomalocaris]

A fact: on this planet, no society (except our own for less than a century) has existed without a religion.

A Fact, no societ has existed without ignorance, or without tendency to presume knowledge where such presumption can clearly be seen to be unwarranted.

Now, the New Atheists simply ignore this fact and what it might be (or it is very likely that it is) a sign of:

on communal level, religion increases the fitness of a society.

So, on communal level, does ignorance or pretending to know when one can be seen to not know, increase the fitness of a society?.