The evolution of cold-adapted terrestrial species underwent two main phases. First, the genera of cold-adapted taxa appeared during the Late Pliocene to Early Pleistocene. The modern day and Late Pleistocene cold-adapted species then arose during and after the Middle Pleistocene Transition. These species evolved through one or more of the following processes: out of the temperate zone, evolving in situ, or through montane preadaptation. Palaeogenetic studies are greatly contributing to our understanding of the timings and modes of evolution of cold-adapted species as well as when their specialised traits evolved. The evolution of polar plant and beetle species is claimed to show greater stasis than that of vertebrates, but could instead reflect morphological conservatism that can be tested with palaeogenetics.