Over at PubMed Steven Austad provides a good argument for considering aging as unprogrammed decay rather than a programmed process in the body. This sort of high level thinking about processes and purpose - like the reliability theory of aging - is an important part of effectively directing the research community. "Aging, except in exceptional cases such as the rapid decay and death of Pacific salmon, is not design but decay. The decay of senescence is not due to natural selection's designing hand, but to its absence. The empirical difference between programed and nonprogramed senescence becomes evident when comparing the stereotypical steps leading to death in salmon contrasted with the lack of such stereotypy in most organisms such as humans and mice."
On the other side of this debate Valter Longo and Paola Fabrizio have authored a paper suggesting that aspects of aging in mammals may indeed be programmed. "Programmed human aging is just a possibility. We don't know whether it's true yet or not. But if aging is programmed in yeast, and the pathway is very similar, then isn't it possible that humans also die earlier than they have to?" This discussion is still at the level of educated hand-waving - much more work is needed to settle it one way or another. My suspicion is that the genetics and biochemistry will turn out to be more complex than a simple yes or no.
The recent Betterhumans article on Longo's work gives a more comprehensive background to the debate in terms of evolutionary explanations for aging and the ramifications of Longo and Austad's positions. Check it out.
In Darwinism, natural selection happens on the individual level. Organisms better suited to their environment survive and reproduce, and beneficial mutations lead species to change over time.
In Longo's theory, however, the majority of a population dies prematurely to provide nutrients for surviving members, who have genetic mutations that increase their chances of reproducing.
"We're not saying Darwin was wrong," says Longo. "We're just saying that there appear to be some big missing pieces in his theory."
As I've said before, I'm always happy to see new theories of aging - it shows that scientists are working on the problem.