the caves and their carvings are from indiginous natives who lived in the area hundreds of years ago. that, plus the introduction of these stones (which are thousands of earth years old) seem to indicate that kryptonians have been exploring other worlds for generations.
the speculation makes this superman an almost biblical figure, who was prophesized and foretold for generations.
Kryptonians exploring other worlds makes some sense, with them being all scientific and such.
But Superman being prophesized for generations doesn't (to me anyway). That would mean that the Kryptonians knew that the planet was going to blow up for those generations. Unless Smallville's writers are tweaking that aspect of Superman, that doesn't seem to work. Thoughts?
