If you were making casual conversation as you painted your cave, what would you be saying? The Times has a bizarre feature on Stone Age small-talk.
Do take a look at Professor David Morley's blog, in response to an article in The Times concerning poetry and the origins of civilization. There is a link to the article at the top of the posting.
You may be interested in this overview of the beginnings of English literature from The Yemen Times.
While I am on the subject of linguistics, I would like to mention an article I read about the fact that Shakespeare worked without a dictionary to hand. It is quite a sobering thought. I will give another plug to the truly amazing Save-the-Words site.