The San hunter-gatherers ran with the herd. It follows that their earliest symbolism would be predominantly of animals. Particularly the tastiest ones, the ones easiest to kill, or the ones that filled the most bellies.
The "staff of life," I suspect, in whatever form, is the earliest, most universally worshipped symbol. Hence, in my view, folks who saw stars as a kind of "staff of life" most likely were sea-people or dwellers on a flat, featureless plain. This is not to say that such symbolism was not syncretized with other traditions, as Lee McGiffen suggests, later on.
Those comparatively few passages which might be interpreted as astral symbolism didn't enter the bible until after the Torah. Ezekiel's wheel is one such example, yes.
Ps. I haven't read the DaVinci Code for precisely the reasons you stated. After reading an infomercial about it in a mainstream newsweekly, I figured it would just tick me off. I could be wrong though . . . :)