INEVITABLE PROPERTY. “Even when cells divide symmetrically, unicellulars readily evolve a state of asymmetric, unequal distribution of cellular damage among daughter cells. However, as soon as such an asymmetry evolves, aging evolves. Thus, aging – despite remarkable variation in the duration of life among different species – might be a fundamental and inevitable property of cellular life.”
http://www.nature.com/scitable/knowledge/library/the-evolution-of-aging-23651151