A historian is a person who researches, studies and writes about the past, and is regarded as an authority on it. Historians are concerned with the continuous, methodical narrative and research of past events as relating to the human race; as well as the study of all history in time. If the individual is concerned with events preceding written history, the individual is a historian of prehistory. Although "historian" can be used to describe amateur and professional historians alike, it is reserved more recently for those who have acquired graduate degrees in the discipline. Some historians, though, are recognized by publications or training and experience. "Historian" became a professional occupation in the late nineteenth century as research universities were emerging in Germany and elsewhere.