Cave dwellers singing

I love to find articles about life and cultures of peoples from all eras, and this one is especially cool. Turns out the cave pictures correspond to the places in caves with the best acoustics, and some of those locations required them to crawl through low tunnels to find. I especially like the idea that they may have relied on essentially echolocation to find these--I've seen some fascinating stories about blind people training themselves to rely quite nicely on echolocation. Also, the fact that the echoes at times resemble the animals in the pictures is very intriguing.