Death is a necessity. If we look at aging from the point of view of evolutionary adaptation, it is clear that it serves a telenomic "purpose". The lifespan of each species is optimized for environmental conditions. Humans have programmed cell death that limits their lifespan to ~100. Other species have other lifespans according to their evolutionary niches, and some species are effectively immortal. It is within our own individual short-term self-interests to prolong life indefinitely. However, it is very clearly NOT in the best interests of society, nor the global ecology, for humans to be immortal. Humans consume vast resources, in great disproportion to their contributions to the greater environmental milieu. Someday, if and when humans (or some form of cybernetic organisms) become vastly more efficient, intelligent, and compassionate, it may be viable to consider immortality. But clearly, technological progress has far outstripped our understanding of its implications. Do we really want a world filled with creaky, old, rich people who never relinquish power? Because it's self-evident that, under the current societal conventions, immortality will not be available to the underclasses. This path eventually leads to a bifurcation of the species reminiscent of H.G. Wells.