The Pampas deer are part of the New World deer, another term for all South American deer species. Fossil records indicate that New World deer traveled to South America from North America as part of the Great American Interchange around 2.5 million years ago, following the formation of the Isthmus of Panama. It is believed that they rapidly evolved into different species, with only a few surviving today. Due to the large continental glaciers and the high soil acidity in areas where there were no glaciers, a huge part of the fossil record has been destroyed, so there is no indication what the New World deer used to look like. Fossil records begin with clear differentiation and are close to what they look like now. The Pampas deer evolved as plains dwellers. Their direct ancestor first appeared during the Pleistocene period (the Ice Age) during the Pampean Formation.