Pleistocene rewilding is the advocacy of the reintroduction of descendants of Pleistocene megafauna, or their close ecological equivalents. An extension of the conservation practice of rewilding, which involves reintroducing species to areas where they became extinct in recent history (hundreds of years ago or less). Paul S. Martin (originator of the Pleistocene overkill hypothesis) states that present ecological communities in North America do not function appropriately in the absence of megafauna, because much of the native flora and fauna evolved under the influence of large mammals.