Well...I guess I'm spitballing here. But by applying the selfish gene theory to aging I keep coming back to this: perhaps people had an advantage to live longer in that it created a larger "genetic team" for an individual.

For instance--one person is descended from people who pass away at 25. They have their parents looking out for them, and perhaps an aunt, uncle, siblings. All people who have a vested interest in the proliferation of that person 1's DNA.

A second person has relatives who live to be fifty. They have another entire generation of people who selfishly want their DNA passed on (therefore those relatives would protect and nurture person #2). In a scramble for limited resources during the EEA it seems that would be an advantage on many levels.

The notion that people typically died at the age of 25 or 30 is simply false. The calculation for average life expectancy at birth includes the very high number of infants that died in Medieval Europe. At no time -- from prehistory until now -- has a 30 year-old been "old." Think of "three score and ten" in the Bible. Human life span has been over 60 since we emerged as a species.

Understanding the mechanics and evolution behind aging has always been a fascinating and important issue, but it has never been a 'problem' for Darwin.

I would also like to comment that there is not a consensus among evolutionary biologists that the two theories of aging discussed in the article can account for or adequately explain aging in part or in whole.

It is correct to state that most people did not die at the age of 25. Life expectancy is an average, which is calculated in part on the high frequency of infant and child mortality. That said, it remains true that long life is not necessary for human survival. If age 30 were an upper limit for survival, biologically we would do fine, although And an expectation of early mortality led--until very recently--to early marriage and reproduction civilization would likely be less advanced. It was no accident or scandal that Juliet was 13, and Romeo not much older.

I agree that evolution is not a problem for Darwin. Considering it might be was a rhetorical device. It is interesting to at least consider traits related to aging are not obviously as simple to understand as the selection of traits necessary for reproductive success. I agree too that there are other theories of the evolution of aging, but the mutation accumulation and the antagonistic pleiotropy theories where a good place to start.

Whatever the evolution of aging, it's prevalence among the population is a relatively new phenomenon. Obviously, the ancients could not have written about senescence if they had no experience with it. But what was rare is now common.

Thanks for all your comments.

"We apparently age because the genes for aging are either neutral for natural selection or the negative side effects of genes that earlier in life promote survival and reproduction"

There is one more possibility: extended lifespan is selected against because of decreased benefits for the species despite benefits to the individual.

Lifespan may be related to the frequency of each generation which in turn is related to the evolutionary rate i.e. a longer generational span would imply, all other things being equal, a decreased rate of evolution and therefore a greater risk of failure to adapt to changing environmental conditions.