The existence of marsupials in Australia and New Zealand prove

According to Darwin, Marsupials were considered inferior with respect to placentals. These species thrived where there was no competition or in other words in the absence of natural selection. Marsupials existence in Australia and New Zealand gives us clue about the geological period and we get evidence that these continents were joined long ago. As per continental drift theory around 30 to 40 million years ago, South America and Australia were joined in the Southern hemisphere and it is believed that marsupials could have migrated between these islands which proves both the continental drift and the related geological period.