...whether or not prehistoric humans experienced "spirituality?" Of course, I don't know, but I'm guessing that shamans reproduced at a rate greater than the average.

If you're claiming that science and art grew out of religion, then you also have to claim that atomic bombs and graffiti are the results of religion. I don't believe it. Some art was inspired by religion, and certainly some of the earliest scientists were clergymen of some sort, but for every instance where you can point to a Gregor Mendel, I can point to a Galileo. In other words, churches got in the way of science just as much as they promoted science.

You can't claim that morality is only a result of religion. Morality, no less than any other human behavior, is an evolutionary construct. We have an innate sense of right and wrong. May I point out again how many church-sanctioned behaviors we currently recognize as being immoral--slavery and various wars of conquest pop immediately to mind. The current religious jihad against equal rights for homosexuals strikes me as highly immoral, yet we're instructed to "tolerate" these intolerant beliefs as being part of people's religious tradition. My point is not that religion is evil, but that it is like every other human behavior--that is to say, human, with good and bad points. I do not see religion as a force for good, on balance, but just as an irrational belief that sometimes--often--stands in the way of real progress in improving the human condition.