The Early Archaic period in Pennsylvania corresponds with the end of the Younger Dryas climatic episode and the beginning of the Holocene episode or the modern era at about 11,700 calendar years ago. This is a very interesting time because it witnessed the most significant environmental change of the past 40,000 years, although some argue that the current episode of global warming will turn out to be even more significant. Additionally, we see radical changes in projectile points from the unique fluted points of the Paleoindian period to the more common notched points of the Archaic period. During the Younger Dryas, fluted points in the Northeast evolve from Clovis into points with longer flutes and a fishtail shape eventually leading to a decreased emphasis on fluting and finally to leaf shaped points with no fluting. Rather quickly, around 11,700 calendar years before present (BP), notched projectile points such as Thebes, Charleston, Palmer, and Kirk appear.