If the earlier date takes precedence, then which incarnation of a supreme being is supposed to be disproved? Roman deities were preceded by Greek, Greek by Egyptian, Egyptian by Minoan, Minoan by Babylonian... and that's as far back as I've read. This, of course, doesn't take into account far Eastern religions. And that's only the organized ones.

Disproving something presents a problem. Take, for example, disproving the existence of Minotaurs. You could prove they did exist by finding remains, but, because you haven't found any, you can't definitively say they did or did not exist. That's why religion stresses 'faith' and not 'proof'.