Just 'cos I'm dogmatic that way, I will delurk to point out that evolution is a blind mechanism and not in any way purposefully directed, so there's no reason whatsoever that one couldn't have a "religious experience trigger" evolve as long as it wasn't actively detrimental to reproduction. There's a tendency on practically all our parts--I've done it plenty, god knows--to fall into the verbal trap of saying "this evolved because..." but in fact things just plain evolve, due to mutation, and those who evolve the more useful stuff get the lovin'.
That said, I can see any number of possible scenarios whereby religious experiences could evolve by accident. Supposing, for the moment, that we're saying it's caused by chemistry in the brain--if enzyme A and neurotranmitter B are both handy things to have around the brain, but once in a blue moon, one misfires and they combine and make Hallucinogen C and you meet God--well, assuming that you do not damage your reproductive possibilities in the ten minutes that you're meeting God, there's no reason that A & B would be selected against. (If, on the other hand, you were consistently eaten by a saber-toothed tiger in that ten minutes, this would be a distinct pressure against.)
Related, if stress chemical A does helpful things under one scenario (i.e. I'm cold!) and stress chemical B does helpful things under another (I'm bleeding!) and there's a whole stress chemical array that the brain has evolved to release according to various stresses, (I'm fighting! I'm starving! Etc!) and then one DIES and the brain, in a panic, starts throwing any switch it can get its grubby little lobes on in that last couple seconds, and stress chemicals A-Z flood the body, coexisting in ways they don't do under normal function, why couldn't they lead to an NDE? Sensations of flight, bright lights, and euphoria are all pretty common effects, god knows, you can get them all on a tab of acid, and LSD's got nothin' on the stuff already rattling around the brain stem.
All of this is pure speculation, I hasten to add, my knowledge of brain chemistry pretty much stopped with "The Dragons of Eden" but nevertheless, there are tons of scenarios that I can come up with before coffee whereby one might evolve the capacity to have something that seems like a religious experience purely by accident.
One final example--there was a Saint Hildegard, back in the day, who had what some scholars now suspect were classic migraines, of the variety that used to be called "migraine with aura." I get 'em myself--mine have bizarre visual flaws, like your field of view being shot through with jittery neon herringbone cracks, a sense of...mm...disassociation, I guess is the best term, and acute loss of peripheral vision. (On the bright side, they don't hurt anything like a regular migraine, which is a prime example of things having evolved that drop you like a rock, but, hey, as long as you can still reproduce...)
Now, me, I say "Hey, migraine, better take some Percogesic and go to bed." Saint Hildegard interpreted it as ecstatic vision, thought that she was witnessing the battles between angels and demons, and drew some fairly bizarre pictures that neverless have the spiky visual-flaw look that I recognize--if I tried to make a woodcut of what I see with a migraine, it'd look like that. This doesn't require any religious experience center to the brain at all, it's just one of the standard malfunctions, but it's entirely possible to interpret it in a religious framework.
And that's enough outta me.
