Kids: Australia, Land of Marsupials
Photo: Flickr user ximenatapia
Why are marsupials concentrated in Australia?
A million years ago, a supercontinent called Gondwanaland was breaking up into the separate continents that we know as South America, Africa, India, Antarctica, and Australia. At the same time, mammals were branching off into two major groups – “placentals,” which develop in their mothers’ wombs, and “marsupials,” which continue to develop in their mothers’ pouches after they’re born.
According to the fossil record, early marsupials – the ancestors of today’s kangaroos and koalas – colonized Antarctica and Australia. Meanwhile, by about eighty million years ago, marsupials and placentals both were roaming the Americas, as well as Asia. In a fight, the placentals had the edge. The marsupials’ offspring were more vulnerable, and the marsupials had less vocal ability than the placentals – so they couldn’t organize themselves socially or even call out in danger.
Today there are still many marsupials in South America – and at least one species – the Virginia Opossum – in North America. But it’s widely believed that marsupials thrived in Australia mostly because they were sheltered from competition.
