Gregory Cochran has written something on aging. I'll post some selected parts, but you should read the whole thing, which is pretty short.

Theoretical biology makes it quite clear that individuals ought to age. Every organism faces tradeoffs between reproduction and repair. In a world with hazards, such that every individual has a decreasing chance of survival over time, the force of natural selection decreases with increasing age. This means that perfect repair has a finite value, and organisms that skimp on repair and instead apply those resources to increased reproduction will have a greater reproductive rate – and so will win out. Creatures in which there is no distinction between soma and germ line, such as prokaryotes, cannot make such tradeoffs between repair and reproduction – and apparently do not age. Which should be a hint.

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In practice, this means that animals that face low exogenous hazards tend to age more slowly. Turtles live a long time. Porcupines live a good deal longer than other rodents. [...] Organisms whose reproductive output increases strongly with time, like sturgeons or trees, tend to live longer. The third way of looking at things is thermodynamics. Is aging inevitable? Certainly not. As long as you have an external source of free energy, you can reduce entropy with enthalpy.

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In principle there is no reason why people couldn't live to be a billion years old, although that might entail some major modifications (and an extremely cautious lifestyle). The third way of looking at things trumps the other two. People age, and evolutionary theory indicates that natural selection won’t produce ageless organisms, at least if their germ cells and body are distinct - but we could make it happen.

This might take a lot of work. If so, don’t count on seeing effective immortality any time soon, because society doesn't put much effort into it. In part, this is because the powers that be don’t know understand the points I just made.

Nothing entirely new to me here, but it's always good to see another scientist come out in favor of aging research. Also, note that the Latin text on the top of Cochran's website is omnes vulnerant, ultima necat, which means approximately, "Each second wounds, the last kills."