A quick map of the South Pacific I found.
So if Antarctica was populated in an earlier epoch, when it wasn’t surrounding the South Pole, and some people there had some warning of, or survived the cataclysm that caused the pole shift, they would have sailed away to the nearest temperate land which would have been South America and Australia. And it would not be a surprise that they had things in common.
ML/NJ
A quick map of the South Pacific I found.