Prehistory is defined by the Oxford English Dictionary as the period of time before written records began. The transition from prehistory to history has occurred gradually at different times in different places. The essential sources of prehistoric information include archaeology, anthropology, biology and geology. In recent times, historians have developed methods of assimilating this information into the historical record so that credible theories now exist about events preceding the written record. Prehistory is essentially about early human existence, based largely on archaeological and anthropological findings, but there have been extensive researches into the prehistory of Earth, using geological evidence, and pre-human life, based on biological findings.
- Oxford University: Oxford English Dictionary, 11th Edition. Oxford University Press (2004).