ADAPTIVE SENESCENCE. “Clearly it can be adaptive for a large organism to cause the senescence of specific organs or structures, such as leaves on a deciduous plant. Whole-organism senescence leading to death is more puzzling, and explaining it has been a long-standing challenge. If a large organism can build itself from a single cell, why can it not maintain itself once built? Or can organismal death actually be adaptive in some cases, in the sense of increasing Darwinian fitness?”