Prehistory can be said to date back to the beginning of the universe itself, although the term is most often used to describe periods when there was life on Earth; dinosaurs can be described as prehistoric animals and cavemen are described as prehistoric people. Furthermore, the word prehistory can be said to have special relevance to the study of the human past, as opposed to, for example, that of other animals or the earth itself, and this nuance can be seen from its usage.