EARLY DEMISE. “For most organisms, the natural world is dangerous since it abounds with competitors, predators, pathogens, accidents, and other hazards. It follows from this that in natural populations most individuals die or get killed before they can grow old and suffer the symptoms of aging: thus, individuals have a very small overall probability of being alive and reproductive at an advanced age.”
http://www.nature.com/scitable/knowledge/library/the-evolution-of-aging-23651151