The power of negative [theoretical] results.

In PNAS, Paul Nelson and Joanna Masel present a theoretical result showing that aging in multicellular organisms is inevitable (1). The argument is as simple as it is powerful. Cellular senescence is a well-known consequence of the second law of thermodynamics, due to mutations, epigenetic misregulation, and protein misfolding. Molecular accidents in a cell can happen and they consequently do happen. In unicellular organisms, life is maintained because of natural selection against senescent cells and, thus, at the population level life can continue potentially indefinitely. However, in multicellular organisms, competition among cells has been killed to ensure cooperation among cells and thus the integrity of the organism. Breakdown of cooperation and unchecked competition among cells is known as cancer. Cooperation, and thus limited competition among cells, leads to the accumulation of senescent cells, while competition among cells kills the organism because of a breakdown of cooperation.