religion has served as a terminal value

Has it? I'd think of it as serving as an instrumental value for the terminal value of going to Heaven/not going to Hell, and earlier as an attempt to control stuff like the weather (earlier? there are plenty of people who still believe that prayers are also granted in this world, not just in the afterlife), or (for some people) as an instrumental value for binding communities/enforcing social norms. I'd guess that people worshipping deities just for the sake of it without expecting anything in return have been a minority.

But don't feel bad, all our genes arose by mutation if you trace them back far enough, and we can say that about most memes as well.

Right. OTOH, saying “human eyes are brown” on the ground that blue eyes arose relatively recently (not as recently as irreligiosity, but still) would sound kind-of weird to me.