Space and time: The two dimensions of Artiodactyla body mass evolution

Thus, there is strong evidence that the evolution of body size in even-toed hoofed mammals was influenced by climatic changes, and by an overall tendency to grow larger, mostly in coincidence with the vegetation shift from forested to grassland biomes which characterized the second half (Neogene) of the Cenozoic. Although Cope's and Bergmann's rule in mammals are often portrayed as having climate change as a common explanation, our data suggest they are mechanistically separate phenomena.