I'm really interested in the whole "real food" movement, although I haven't yet made that leap when it comes to our diet. It does make sense that our bodies would do better eating foods that they've been digesting for thousands and thousands of years. Then again, when I look at how long we live now compared to the short lives our ancient ancestors lived, I wonder just how big of a deal our processed foods are.
Then I looked at the issue of life expectancy a bit closer. Sure, life expectancy has skyrocketed since "the olden days" (basically pick any time in history), but we really can't give all the credit to our diet. This is more due to modern medicine and public health than to say the advent of Oreo cookies, as much as I'd like to attribute cream-filled chocolate wafers with incredible powers of longevity.
What is even more interesting to me, though, is the fact that human lifespan is a fairly constant number. For example, the maximum human lifespan has remained at 105-122 throughout recorded history (the fantastic numbers of those Old Testament patriarchs aside). Most of the increase in human life expectancy is due to the dramatic reduction in infant/childhood mortality rates. So if you look at the life expectancy of everyone at age 5 (instead of at birth), you wouldn't get such a huge difference over time. For example, in ancient Rome when a child was born their life expectancy was only 25, but if they made it to age 5 their life expectancy was 48.
Life expectancies have certainly increased and will probably continue to do so (to a certain point), but it's really difficult to pinpoint how different factors influence this. I wish there was some snazzy social science equation that could crank out numbers for every factor that might influence lifespan (e.g., infant mortality, public health, modern medicine, war, natural disasters, and of course diet). Just how important is our diet? Would we add a couple extra years to our lives if we switched to real food? Hard telling.
Overall interesting food for thought, huh? We live longer, for many reasons, but the difference isn't quite as dramatic as we usually think. I'd really love to see a table of historical life expectancies for children at say age 5, as opposed to from birth.