just something i remember watching on youtube, apparently the polar ice caps are no oldder than 4000 years old, and that could be evidence of the last polar shift, which supposedly happens every 3600 years or so. some scientist said that HE BELIEVED that the north pole was 'somewhere north of wisconsin' and the south pole was somewhere in the pacific ocean.
this would explain why mammoths died out, because they would have been a tropical animal (i.e. ON LAND, not ice). and plants were found in the throat of the mammoth dug up in siberia. antarctica had animals 4000 years ago. and the polar shift would have changed the climate and caused what some consider a 'cleansing'
None of the above is what I came up with, before you guys flame away. I do believe that philosophers do know something we don't, though. I'm not going to debunk any theories because there are too many things we don't know about the world (and universe) we live in for us to start making assumptions.