So, this is probably opening a can of worms, but is the Indo-European mythology pre-1600?
That seems like a laughable question, in that we are talking about beliefs from 4000 or more years ago, except that we have no direct attestation to the myths and languages of the early Indo-Europeans. Instead, all Indo-European mythology is a speculative reconstruction by archaeologists of the possible beliefs of early Indo-European peoples based of common elements found in multiple belief systems that we do have some textual attestation to. In other words, it's well informed guesswork and the result is a body of beliefs that may be close to some ancient body of beliefs (or not) but which in all likelihood is sufficiently different from whatever the real body of beliefs actually was, that it could be said to have only to come into existence within the last 150 years.