Presented by Dr Brandon Menzies from School of BioSciences The University of Melbourne
Marsupials have dominated the Australian landscape for the past 50 million years and still account for about 58% of its terrestrial mammals. However, the well-known legacy of mammal extinctions since European arrival, including that of the iconic Tasmanian tiger or thylacine, is a tragedy not just for posterity but also for our understanding of evolution. The thylacine was the largest extant carnivorous marsupial at the time of European settlement and remains the greatest example of convergent evolution within the mammalian lineage. That is to say, its size, body structure, and dentition were nearly indistinguishable from that of the dog or wolf. The presence of a pouch in females and the posterior positioning of the penis relative to the testes in males were the only obvious features to distinguish it as having evolved from the ancestors of the Tasmanian devil and kangaroos rather than those of wolves and man. The tale of the thylacine is one that should inspire young scientists to understand more about our unique marsupial fauna. Indeed, recent analysis of the genetic diversity of many populations of marsupials, including the Tasmanian tiger, emphasizes the vulnerability inherent in their DNA. Yet, the thylacine may not have taken all of its secrets to the grave. New technologies are allowing us to piece together small fragments of its genetic code so that we will soon be able to compare the sum of those pieces, the thylacine genome, with those of its doppelganger, the dog. We may soon understand the molecular processes that drove the remarkable convergence in the appearance of this unique mammal with that of mans best friend.