"The Singing Neanderthals" by Steven Mithen contains some very interesting speculations about the origins of language, and it's very worth reading even if (like me) you don't agree with all his conclusions.

Much later than the origins of languag, but still demonstrating its mystical power: A few tears ago, an archaeology TV program (forgotten which one) showed a demonstration of resonances in a neolithic tomb. When his sound generator hit the right frequency, the dust at the maximum- velocity points of the resonant wave rose from the floor in vaguely human shapes.... truly spooky, and a shaman could have used this phenomenon to show his power of "raising the spirits" by low chanting.