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etter if the older generation doesn't stay around forever competing<br />

with younger generations for scarce resources.<br />

In terms of what happens physiologically, there are two<br />

main contributors to aging.<br />

The first is the accumulation of biological defects. Viruses<br />

and disease take a toll even after healing; UV rays slowly but<br />

inevitably damage DnA; and proteins, cell structure, and the<br />

neurons which hold memories all degrade over time due to<br />

thermodynamic molecular disruptions and invasions by other<br />

species.<br />

The second is the aging process itself. The organism develops<br />

to maturity and ages in stages according to a genetically<br />

determined life plan. Muscles atrophy, bones brittle, and metabolism<br />

changes. But the life plan has never run more than<br />

eighty years until recently, and evolution only ever optimized<br />

the first forty years or so. So humans are in new territory that<br />

is poorly understood, and which evolution has never had a<br />

reason to fine tune.<br />

It may be possible to slow or stop some of the genetically<br />

determined aging processes. While this may not be good for<br />

an overpopulated planet, it is sure to be popular with those<br />

that can afford the medical intervention. Let's just hope the<br />

social security system holds out!<br />

[1] There is evidence that even in "symmetric" cell division,<br />

one child cell may be slightly "younger" (less prone to<br />

death) than the other. See: Stewert eJ, et al (2005). Aging<br />

and death in an organism that reproduces by morphologically<br />

symmetric division. PLoS Biology. http://www.plosbiology.org/article/info%3Adoi%2F10.1371%2Fjournal.<br />

pbio.0030045<br />

http://www.quora.com/l/boq-paul-king<br />

223

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