Have you ever wondered why do kangaroos live only in Australia? There are more places with such a climate and conditions. What appears to be an explanation is this: Kangaroos are mammals with a bag (Latin Marsupialia). The first mammals appeared in the age of dinosaurs, believe it or not. With the climate change on Earth, the dinosaurs disappeared, while mammals were breeding and evolving differently. Mammals with placentas have evolved more rapidly than mammals with a bag. Thus, the marsupials from the many parts of the world were extinct, because they couldn't survive in the struggle with other mammals. That, however, did not happen in Australia and South America. Scientists believe that Australia used to be linked with Southeast Asia, probably by a number of islands. Marsupials most likely spread to Australia at a time when there was no more placental mammals at all. As they had no rivals, they have evolved and developed in different directions to become what they are today.
