Prehistory refers to the period of human history between the first known use of stone tools by hominins around 3.3 million years ago and the beginning of recorded history with the invention of writing systems. It is called prehistory because it refers to the time before history, meaning before the invention of writing. Prehistory is any time that occurred before human societies developed writing systems. Scholars define prehistory as events that occurred before the existence of written records in a given culture or society. The Stone Age, which is the period before writing and civilizations, is extremely valuable to our understanding of our earliest hominid ancestors. Prehistory is different from history not only in terms of its chronology but also in the way it deals with the activities of archaeological cultures rather than named nations or individuals. Restricted to material processes, remains, and artifacts rather than written records, prehistory is anonymous.