At the end of a recent post, I cited the following study: Fitness cost of extended lifespan in Caenorhabditis elegans.
Abstract: An insulin/IGF-I-like signalling pathway determines the rate of aging of the adult nematode, Caenorhabditis elegans. Mutations in genes encoding this pathway can result in a doubling of lifespan. While such mutations may appear to have little effect on development or fertility, evolutionary theory predicts that large increases in lifespan will not be optimal for fitness. We demonstrate by laboratory natural selection that partial loss of function of the insulin receptor-like protein DAF-2 results in dramatically reduced fitness even under laboratory conditions. Despite long-lived mutants appearing healthy, they exhibit a heavy fitness cost consistent with an evolutionary theory of aging.
Some excerpts from the discussion:
... To test the fitness of this long-lived variant, we undertook laboratory natural selection experiments as previously described in which we mixed wild-type worms with daf-2 mutants and cultured these populations over multiple generations. Consequently the wild-type and daf-2 mutant worms were subject to identical environmental conditions and were directly competing for resources. We found that there was a significant cost associated with the daf-2(e1368) mutation even under a regime of constant food, with the daf-2 mutation becoming extinct in all populations in only four generations. This rapid extinction suggested a major fitness cost.
... Our results demonstrate that early fitness traits rather than lifetime fertility are important when assessing the possibility of trade-offs between longevity and Darwinian fitness.
... In many longevity mutants, fitness costs may be readily apparent, such as those with altered development and greatly reduced fertility. Our results demonstrate that even in instances where the mutants are reportedly healthy, their increased longevity is still associated with reduced fitness, as predicted by the AP theory of aging. We conclude that even though the longevity mutation confers apparent benefits on the individual in terms of lifespan and stress resistance, competitive fitness is lowered, resulting in rapid extinction.
There have been a number of discussions on this worm, longevity research, etc. over on Paleo Hacks. The bottom line is that longevity is not consistent with evolutionary theory. It seems to me that respect, reverence and caring for the elderly is a uniquely human trait, and likely a neolithic one at that though I'll leave that to the more knowledgeable to ponder. Wild animals don't support their aged to live their maximum physiological lifespan. As this study demonstrated, the longevity mutants die out when forced to compete with wild-types for resources -- apparently even if those resources are not scarce. So while it might be intriguing and interesting for Mark Sisson to imagine that Grok joined the hunts into his 70's, it doesn't sound like that would have realistically been the case to me.
When Ron Rosedale flickered across my radar screen, I was struck by the "televangelist" like picture on his website. He has another icon with a light shining from behind him that he uses on comment boards about the internet. The longevity-seekers have always struck me as somewhat cultish. The masses are urged to follow their lead with the promise of a long life similarly to promises of eternal life. Despite ample evidence to the contrary, Rosedale sticks to his "everyone is a diabetic" preachings invoking leptin spikes and merely repeats the same arguments over and over. If you read the lengthy safe starch back and forths, that's all he does. Cite the same study that doesn't even make his point, taking one sentence from the study out of context. In any case, Rosedale is a newcomer to paleo circles, hawking his longevity schtick. Only he himself will tell you that longevity is not paleo. Jack - Leptin Man / Dr Duvet / Quack Frost / never too many nicks - Kruse MD, DDS is also big into longevity. His "Holy Trinity" is based on calorie restriction and cold adaptation for longevity. He too has been welcomed into the paleo movement with open arms by the movers and shakers despite his message having nothing to do with paleo other than that he advises we eat an undefined paleo diet.
So there seems to be a bit of an unholy alliance forming in the paleo (and greater ancestral) community. Jack's inspirational message at PaleoFX was basically that there's no room for infighting in this community. I say there's no room for tolerating quackery and woo woo, because if the goals of getting nutritional information/recommendations changed is to ever be achieved, the "movement" that accomplishes this MUST have credibility.
The "paleo diet", whatever that was, would from an evolutionary perspective be one that would favor reproduction over longevity. So when you have folks claiming that our paleo ancestors ate XYZ and we evolved or our genetic makeup is predisposed to thrive on XYZ, that means XYZ is best for "fitness" and survival. When folks come along and then claim that XYZ diet is optimal for longevity, there is a disconnect. I don't see how you can have it both ways. And if one is going to advocate a different diet for different stages of life, this too would seem counter to common sense. The foods available to our ancestors didn't change. If there really weren't carbs to be had for our ancestors, then they weren't eaten at any age. And if our ancestors ate the fat of a carcass preferentially, what did the older paleo humans get to eat? Did they save the fat for them or did they throw them the meat they would have otherwise left to rot? Too many "mismatches" of reason in my opinion.
Although not the topic per se of this post, I struggle with disconnects between what is healthy and what promotes longevity. I guess the crux of that is what happens or what we're at risk for as we age:
- Insulin sensitivity declines, RQ decreases indicating decline in glucose oxidation
- Muscles atrophy
- Bones demineralize
All of which are not prevented and may even be contributed to with calorie and/or protein restriction and/or carbohydrate restriction necessitating a very high fat diet -- in other words a supposedly life extending diet. The elderly die from falls and/or never recovering from broken bones every day in this country. The nursing homes are filled with emaciated deteriorating humans who look like a child could snap them in half. I don't want to be overly morbid or depressing here, but these are the things I think about as I'm aging. Whatever I've done so far, including low carbing, has sustained a goodly amount of lean mass. In a way this gives me a buffer for experimentation and it would take a lot to make myself at risk for osteoporosis and such. I guess in a way, the paleo diet -- if we can ever agree on what that was -- cannot give us many clues on the optimal human diet as we age to maximize not only lifespan, but the quality of that life. I believe, based on comments made here in the past, that the latter -- quality -- is what most of us are seeking answers to how we maximize that through diet/lifestyle. Moving forward .....