Koalas may look gentle today, but they have evolved from deadly ancestors, study stated. Modern koalas evolved from a lineage that included lethal predators such as the marsupial lion, Thylacoleo carnifex, which lived 2-3 million years ago and once dominated Australia's forests and giant wombats. Protein analysis also links their lineage to giant herbivores like Zygomaturus and Palorchestes.