ABSTRACT
Aging and programed death has deep evolutionary roots and is ubiquitous in unicellular and multicellular organisms. It has been proposed that the evolution of programed death in unicellular organisms was a prerequisite step for the emergence of multicellular structures. All organisms live in ecosystems and the organization of an ecosystem is characterized by mutually advantageous interactions between diverse species across multiple trophic levels. Multilevel selection acts to optimize the fitness of the constituent individuals and species within an ecosystem as well as the fitness of the ecosystem as a whole. Within the context of the ecosystem, aging and death represent adaptive phenotypes through which resources including information can be transferred between organisms and by which relative species abundance can be regulated. Species abundance and diversity are the primary determinants of ecosystem functionality. All organisms modify their environment to some degree through, for example, the building of nests, hives, or burrows. Humans, through cultural practices, have acquired the capacity to modify their environmental space to such an extent that these modifications are now having a global impact. In addition, these environmental modifications are shaping human evolution through the process of gene–culture coevolution and indirectly altering the evolution of other species sharing the same environmental space.
