The continent of Australia is home to many exotic mammals, including hopping kangaroos, egg-laying platypus, spiky echidnas, carnivorous Tasmanian devils, and cuddly koalas. The ancestors of these present-day Australian mammals lived on the Gondwana supercontinent (the ancient landmass that later fragmented and drifted apart to eventually form the present continents). Splitting of the Gondwana landmass, starting about 145–200 million years ago, separated mammals in Australia from mammals in Africa, South America, India, and Antarctica. Vast oceans between the modern continents created geographical barriers, allowing the independent evolution of the unique mammalian fauna of Australia. It is possible to trace these historical events and understand the relationship of animals with the use of the molecule common to all living things: DNA.