Recorded history or written history is a historical narrative based on a written record or other documented communication. It contrasts with other narratives of the past, such as mythological, oral or archeological traditions. For broader world history, recorded history begins with the accounts of the ancient world around the 4th millennium BC, and coincides with the invention of writing. For some geographic regions or cultures, written history is limited to a relatively recent period in human history because of the limited use of written records. Moreover, human cultures do not always record all of the information relevant to later historians, such as the full impact of natural disasters or the names of individuals. Recorded history for particular types of information is therefore limited based on the types of records kept. Because of this, recorded history in different contexts may refer to different periods of time depending on the topic. The interpretation of recorded history often relies on historical method, or the set of techniques and guidelines by which historians use primary sources and other evidence to research and then to write accounts of the past. The question of the nature, and even the possibility of an effective method for interpreting recorded history, is raised in the philosophy of history as a question of epistemology. The study of different historical methods is known as historiography, which focuses on examining how different interpreters of recorded history create different interpretations of historical evidence.