I wonder though if the lack of evidence for belief from very early hunter-gatherers is actually proof of a lack of belief.
No, it's not, but it is an intersting idea. Foragers don't settle, so we can't find areas rich in artifacts. They also did not have many possessions since they generally lived in the open and moved on quickly. Then there is the issue of the highly symbolic nature of religion. Symbolism is so subjective, that we really don't understand the meaning of much of it. We can make guesses. We can look for other clues, but we will never know for sure. We can find an area with a lot of flint chips, and we can surmise that they stopped here and made tools. But without settlement, there will be no accumulation.
Most artifacts are lost to the ages. Foragers are the trickiest. We know from more modern foragers that they tend toward magic. They may also gravitate toward believing in spirits and the thought that inanimate objects and animals have spirits. Foragers' religion is very different than the religion of horticulturists and later agriculturists. Those gods would focus on the growing seasons, and the sun would be very important. And those people settled and built places of worship. Lot's of evidence.
So it's a tough call. I've been studying anthropology, and I can say that I have not learned about any foraging band that did not have some kind of religion. That doesn't mean they didn't, but clearly their lives are full of questions and often they found themselves at the mercy of nature.
So for the long history of humans, we were foragers. Our religion would have reflected this. Look at the religion of the bible. It's an agriculturalist's religion. A temple, growing seasons and rituals, home ownership etc. If anything, the huge variety of religion proves that the spiritual in not true, because if it were, where is the direction and uniformity? Or does the spiritual simply not care, and left humans to flounder for the answers while expecting acknowledgement?
And claiming that the Hebrew god and Jesus are somehow special and true is laughable. We have millions of years of history, (including archaic humans) including mostly magic practicing foragers, and three thousand years ago some people started putting it in writing---AND IT'S TRUE! LOL And we were wrong for ages and ages before then. It makes absolutley no sense.
But liberal believers will simply write and rewrite these facts and their beliefs until it all fits. In that way, I think it is a great deal harder to make a point with them than it is fundamentalists. Fundamentalists see one way and truth. You can call them on it. Talking to a more liberal believer, and you are trying to catch water in your hand. It is whatever they need it to be, and absolutely no fact will have any effect on that.
Which is fine. I just get cranky when they try to say it is scientific. Once that is out there, the conversation that follows is absolutely dizzy making. They treat science like they treat their belief system---as though it is something that is fluid with no direction and is whatver they need it to be.
NC