The Younger Dryas is an episode in the Earth's history between 12,800 years ago and 11,600 years ago. This is one of the most famous episodes in the history because it is the last cold episode before the Holocene and the megafauna went extinct during this period. There is no one widely accepted theory for the cause of the extreme and sudden temperature drop which occurred in Younger Dryas, but the most compelling one today is the meteorites hypothesis, known as the Younger Dryas impact hypothesis.