When studying about the prehistoric man under archaeology, just as looking into the cultural features, the Archaeologist should also look into the environmental features around. Although the prehistoric man built a culture, as he too is an animal who depends on the environment and the culture he built is also based on environmental facts, the natural environment therefore, is important.
As such the period before writing or the period before the historic period is known as the Prehistoric period. Though the Deepavamsa, Mahavamsa and other literary sources stats briefly of this period, the information given cannot be believed or understood properly. Certain sources describe Yakshyas (demons) and Nagas (snakes) like humans living in the island.