Hi Phil, 
Thank you for that comment. It raised some issues I've been wrestling with. 

Given sufficient time eating them, I think we would eventually become fully adapted to many foods, but as you said, how long that would take is an open question. Another challenge with the Paleofood paradigm is that humans have spread so widely around the globe that each of us may have genes from any of a number of environments, and a full or partial adaptation to some of the foods derived from those various places, but we are unaware of the foods to which we are best suited. I think that while there are several large areas of common ground, regarding our nutritional needs (as articulated in the Paleo perspective) there are also many, often nuanced, variations in each of our individual requirements. So I suspect that our adaptations to some foods are partial, as with the panda. And some of us have genes that are fairly well adapted to particular foods for which most of us would have a lesser capacity. For instance, there may even be people who are fully adapted to eating ground nuts and peanuts, while most of us may be unable to eat them. The most extreme example is peanut allergy.  

Because we were so widespread so long ago, most of us have at least partially adapted to some niche foods. Panda bears, on the other hand, occupy a relatively small environment. They may only be partially adapted to their primary food. I don't know about that. But I suspect that if their adaptation is only partial, they could quickly shift to some meat in their diet, if only because the ancestors they share with other bears were clearly able to eat meats, but perhaps the panda GI tract has reached a point of no return. It is sufficiently altered that such a shift would not be likely. But how many of us would have expected Icelandic ponies to be able to survive eating fish? 

While I agree that partial adaptation is one weakness in the Paleofood paradigm, another, much larger weakness is that most of us are sufficiently different in our genetic heritage, and hence our environmental adaptations, that it is impossible to assert a universally optimal human diet - even if it is strictly Paleo. In fact that is the central thesis of my current writing project. The Paleo perspective only gets us so far. It certainly shows us some common ground, but it misses many of the subtle differences that can manifest in serious illnesses. 

In my book (if I ever finish it) I also argue that we can get a sense of most of the foods to which we are best adapted by carefully following a variety of our own signs such as blood pressure, fasting glucose, HbA1c, weight, ketone body production, energy levels, thyroid function, mental acuity, etc. etc. as we experiment with various diets. I don't know if we can find an optimal diet for each of us, even in that context, but we can get a much clearer sense of what foods cause significant reductions and improvements in signs and symptoms of good health (assuming that those signs and symptoms are, indeed, reliable predictors of health). 

I also argue that there are a number of other factors involved in this complex and elegant interplay between our genes and our environments, which we are rapidly altering without first counting the costs.     

I agree with your central idea, but I think that the larger question is what each of us is best equipped to eat. Further, I do think that nature is interested in optimal health.  In an uncontrolled environment, over sufficient time, those with optimal health will ultimately outstrip less healthy people in survival and reproduction. 

Best Wishes, 
Ron 

-----Original Message-----
Paleo Phil said:

Ron Hoggan wrote: "But I think that the whole idea behind the healthful benefits of paleo foods is that if they were eaten long enough humans developed an adaptation to them."

However, Ron, most people who are doing Paleo seem to want a diet that promote optimal health, whereas nature doesn't care if optimal health is achieved or not, it only works to encourage the survival of those species that can reproduce and take care of the offspring. 

The giant panda is an interesting example of a species that seems incompletely adapted to the main food it eats (bamboo shoots and leaves), despite eating it for millions of years, yet it survived and thrived for millions of years despite incomplete adaptation (perhaps because the bamboo was so abundant for so long and there was little competition), so nature didn't "care" that it wasn't fully adapted.

Thus, it's quite possible that hominins could have eaten groundnuts for millions of years (which they apparently did, based on the evidence) without becoming fully adapted to them (which nearly everyone in Paleo circles seems to accept about peanuts--although eating boiled peanuts, instead of roasted or dry roasted, might produce less deleterious results). Thus, peanuts and other groundnuts may be edible "naked, with a sharp stick," but they may not be optimal and no one knows how long it takes to adapt to various foods. Do you follow me?