Prehistoric Rock-Art Rocks
Around the world, ancient cave scrawls tend to be in hard-to-reach locations. Rock-art acoustician (now there's a job!) Steven Waller thinks its because of the acoustics.

In a recent paper presented to the First Pan-American/Iberian Meeting on Acoustics (held in beautiful Cancun in Dec. 2002), Waller describes how he analyzed over 100 prehistoric sites, including cave paintings and petroglyphs on three continents.

His findings show that echo levels in these art-adorned caves, canyons and rocky cliff faces are significantly higher than places with no art. Waller believes that this is no coincidence; in his abstract he observes: "A variety of ancient legends from cultures on several continents attribute the phenomenon of echoes to supernatural beings. These legends, together with the quantitative data, strongly implicate echoing as relevant to the artists of the past. The notion that the echoes were caused by spirits within the rock would explain not only the unusual locations of prehistoric art, but also the perplexing subject matter. For example, the common theme of hoofed animal imagery could have been inspired by echoes of percussion noises perceived as hoof beats."

According to Waller, an echoed sound is a "psychoacoustic event that would have been inexplicable to ancient humans." He cites the Greeks' nymph "Echo," the Paiute legend of witches who repeat the words of passers-by, and an echo-being in the Book of Hopi's creation myth as examples of the pervasiveness of acoustics in ancient myth.

He urges further study of his hypothesis, as well as conservation of the natural acoustic properties of rock art environments. 

Link to Waller's scientific paper