As scientists continue developing climate change projection models, paleontologists studying an extreme short-term global warming event have discovered direct evidence about how mammals respond to rising temperatures. In a study appearing in Science February 24, 2012, researchers from eight institutions, led by scientists from the University of Florida and University of Nebraska, found a correlation between temperature and body size in mammals by following the evolution of the earliest horses about 56 million years ago: As temperatures increased, their body size decreased. Horses started out small, about the size of a small dog like a miniature schnauzer, said co-author Jonathan Bloch, associate curator of vertebrate paleontology at the Florida Museum of Natural History on the UF campus. Whats surprising is that, after they first appeared, they then became even smaller and then dramatically increased in size, and that exactly corresponds to the global warming event, followed by cooling. It had been known that mammals were small during that time and that it was warm, but we hadnt understood that temperature specifically was driving the evolution of body size. The PETM is really important, because it marks the beginning for the first appearance of several major groups of mammals, including crown-group primates (ancestors of modern primates) and the first even- and odd-toed modern ungulates (mammals with hooves), Bloch said. This sets the scene for the entire diversity of animals we see on the planet today. Funny how science supports science.