In Michael Rose's talk (about his Methuselah flies and what they mean for longevity) at the recent Immortality Institute conference in Brussels, he talked about the three diet regimes that humans have lived under: Hunter Gatherer (2.5M years(?), more gatherer at first, later more hunter); Agricultural (10K years), and Industrial (100 years). He said that humans adapt to new environments in 30-60 generations. 10,000 years is ~500 generations, which should be plenty of time for deleterious genes to be flushed out if they occur much prior to the end of reproduction, (35 years for women, older for men? Maybe an average of 40?) We clearly haven't had time to adapt to the modern 'industrial' diet.
Rose's hypothesis raises a very interesting point about the relationship between evolutionary pressure and diet. As you move from the start of your reproductive period to the end, the evolutionary pressure against possession of a deleterious gene decreases, when averaged over a population. In fact, because humans aid in raising their children and grandchildren, the pressure to drop deleterious genes actually continues (at a much lower level) somewhat beyond the end of reproduction. The upshot of this is that as you get older, it becomes more important to switch to a Paleo diet. Evolution has provided most of us with very good early life adaptations to an agricultural diet, but some of these adaptations begin to fail us later in life, while our ancestral adaptations to a Paleo lifestyle, due to the much longer time we had to develop them, are still active in later life. Rose's prescription for attaining a 'natural' version of the 'biological immortality' of his Methuselah flies is to switch to Paleo after 40. (Earlier if not Eurasian.) You can certainly start Paleo sooner, but it's not as necessary.
If you're in your 20's, you can get away with most anything; certainly an agricultural diet for all but a few of us, and some of us can eat an industrial diet without apparent harm. As you slide through your 30's, you will see things unravelling, as you get fat and your metabolism goes to hell.
The reason I don't quite buy that theory is that older people who have eaten healthy kinda paleo style all their life do not get sick right away if they eat neolithic. THey might experience a period of adaptation, sure, but they don't get diabetes in a year via eating neolithic. So personally I think it is not your age but your lifetime exposure. My own hypothesis is that neolithic foods are like a slow poison. THe more you eat, the sicker you get. Kids now are eating more crap than at any other time in history. Therefore, you are seeing obese young kids with diabeties and fatty liver disease. That didn't use to happen until the 40s. But these kids cannot get away with eating as they eat now, even though they are young. Because they are getting what used to be a lifetime of sugar exposure in what is now just the beginning part of their lives. So they are already sick at a young age. I think damage is cumulative. Keep exposure to a minimum and it never accumulates much momentum. But take massive doses and even the young cannot adapt. There may also be a level that is basically 'safe' and creates minimal damage, that that level is probably diff for each person.
But then again, should we be waiting for signs of damage before changing an habit? It will be interesting to see the first children born and raised entirely on a Paleo diet grow up and develop so we can compare them to the masses.
If his hypothesis stood, it would certainly provide the wiggle room needed for us parents whose children frequently come contact with neolithic foods via classmates' birthday cupcakes, Halloween, party foods, nonpaleo relatives' or caregivers' offerings (even when well-intentioned).
It basically says to me that there is a possibility that as long as I set the stage at home with paleo/primal principles, by the time my kids hit young adulthood - when they can make the dietary choices for themselves - they might have a chance at keeping the paleo inertia going into middle age and beyond, while their above-described childhood neolithic choices might be 'forgiven' by their bodies.
I'll be staying tuned to see what more might come of this.
I think this is one of those cases where the seemingly obvious recommendations via a general or statistical model contradicts reality. The nutritional profile from conception to five years of age is crucial for proper growth. All those paleo-sphere blog posts on malocclusion and dental caries spring to mind. So you need a proper diet, probably for your first twenty years, just to even begin entertaining the idea that you could spend your 20s and/or 30s eating junk, and then you have to go back and eat like your good paleo mother told you to when you are 40 anyway, so why develop all those bad habits?
this is an old post but I found the issue very interesting, though actually could not follow the logic. You said "Rose's hypothesis raises a very interesting point about the relationship between evolutionary pressure and diet. As you move from the start of your reproductive period to the end, the evolutionary pressure against possession of a deleterious gene decreases, when averaged over a population. In fact, because humans aid in raising their children and grandchildren, the pressure to drop deleterious genes actually continues (at a much lower level) somewhat beyond the end of reproduction. The upshot of this is that as you get older, it becomes more important to switch to a Paleo diet."
But if the evolutionary pressure against possession of a deleterious gene actually decreases in older people, then switching to a Paleo diet should be optimal at younger ages, when the pressure is stronger. And you said the opposit...I am confused, could you better better why is it that switching to paleo would be optimal only later in life?
Caveat: I'm basing this answer on your summary rather than Michael's original talk.
Any theory with assumptions needs to first prove those assumptions. In this case, one claim is that we would have adapted genetically (to reproductive-age, at least) to the Agricultural diet. Proof? I would be very interesting in knowing the adaptations and the specific genetic mechanisms.
Digestion of lactose? For some of us, agreed. Lactase. So this covers one food category.
How exactly did agriculturists adapt genetically to glutinous (or any other) grass seeds beyond what would have also applied to our Paleolithic ancestors? Wouldn't those in the Paleolithic have been able to live to reproductive age equally as well as the agriculturists if they happened to have eaten cultivated wheat or rice pre-10,000 BC?