The best argument against strict paleo is that it is impossible. Just about every food we have available today is the product of thousands of years of co-evolution. Let's take a good paleo food for example - say, beef. Ok, cows didn't exist thousands of years ago. They were aurochs then and probably ate differently than cows do today, produing meat with different nutritional elements. This is true for any domesticated animal. How about strawbarries? Undomesticated strawberries were small and extremely tart. You wouldn't like them. Nuts? They were mildly toxic and bitter until humans started to domesticate them. Try an acorn and you will know how nuts used to taste. Potatoes and avocados are from the new world so they're not stricly paleo either. Read Guns Germs and Steel for a decent discussion of co-evolution.

Another argument against strict paleo is that it relies on cherry picked evidence. I don't like Cordain because of this -- he identifies non-paleo foods and then finds what's wrong with them. Putting aside my point that almost all modern foods are non-paleo, this approach has a big problem: there are bad things to say about any food. Spend enough time on the AJCN archives and you will see what I mean.

I think a "modified paleo" is a better diet scheme to defend. Try to fix a few of the more fundamental features of our diet that have changed in ways that really seem (based on robust evidence) to produce disease. Examples include:

1. The omega 3/6 imbalance. Try to balance 3 and 6 and to restrict consumption of both to under 4% of calories, in aggregate.

2. Inadequate vit D. This isn't so much about diet as lifestyle. Thankfully, you can keep your modern indoor lifestyles and still obtain sufficient vit D by taking D3 supplements. I would avoid the excess retinol of cod liver oil, however.

3. Mineral deficiencies. For Westeners, especially ones eating well (like paleo eaters), calcium and magnesium are the most likely deficiencies (calcium deficiency may be simply due to rampant vit D deficiencies and magnesium deficiency is due to fact that it is found in most natural water sources but not in tap or bottled water).

4. Excess fructose. Amounts obtainable from a few pieces of fruit are fine, but eating fruit, soda, and dessert will break you liver - and then your pancreas.

5. Gluten. I think gluten is a problem only for a minority of people. For now, though, I would avoid it on a cautionary principle. There is enough evidence that it is producing disease that it's better to avoid until you know it's not a problem for you - and knowing that isn't possible today (from a practical perspective).

I think the only unique thing to 'paleo epistemology' is the intuition that our evolutionary past is likely to provide a strong model as to what constitutes a healthy lifestyle. It's more of a useful heuristic than a theoretical position or doctrine.

Of course it's a substantive empirical question whether thinking in terms of evolution does provide useful answers to these sorts of questions. Even though everything biological obviously ultimately occurred through evolution, thinking in evolutionary terms doesn't necessarily tell us very much about what's optimal. That evolutionary reasoning does provide simple and powerful answers, is fortunately true. For example, during periods of scarcity we would obviously have to run our metabolism on saturated fat, so it's prima facie implausible that such a metabolic set up would be harmful. Similarly the limits on our evolutionary niche, e.g. omega3:6, potassium:sodium ratio, being fixed, mean that our evolutionary history offers powerful predictors.

Clearly where evolutionary reasoning is most powerful is where we see correlation between evolutionary trends and other harder factors, like limited carbohydrate->the problems of hyperinsulinemia.

One does need to "own" the information and apply it for themselves! It can be a long view towards the truth behind any nutritional approach. You are onto the best bloggers (Eades, Stephan Guyenet, Petro Dobromylskyj, Kurt Harris, Don Matesz), read old posts, read comments, make note of your own confirmation bias and follow tangent discssions that counter what you have come to know/believe. I have read plenty of Matt Stone and Anthony Colpo's, The PCRM, Ornish, T Collin Campbell, etc, writing to see that the "better" bloggers above have a more clear and deeper analysis of the proper nutritional approach.

It took me 30+ years of being passive in regards to health/nutrition, and only 2 years to get proactive and read voraciously to get to a deeper understanding. I can't convince you, and doubtfully any single person, book or blog will. It will be the cumulative education you give yourself that will lead you.

Opposing views are not necessarily idiotic, but often are ignorant. You have to delve in to see for yourself. Other "debates" worthy of looking at are the dust up between T Collin Campbell and Loren Cordain. And Chris Masterjohn's analysis of "The China Study". No easy answer, just lots to read out there!

I think the toughest argument to counter are the extreme animal rights arguments, which are appealing to many people. I have friends who absolutely believe slaughtering animals for food is wrong and it's hard to counter them. Even I have trouble slaughtering animals. The Vegetarian Myth argument that eating grassfed animals leads to less net death doesn't hold much water when you realize that the adorable baby male goats on your professor's farm that are so friendly are going to die. This video addresses the ambivalence even farmers hardened by rural life have about slaughter. Though personally I feel much of the problem comes because the government has regulated large animal slaughter off the farm, which is harder on both people and animals.

At this point I've done slaughter myself. It's not fun, but I was perfectly comfortable eating animals after the slaughter. However, my friend I did it with has been a vegetarian ever since.

I also read Eating Animals and The Face On Your Plate. Maybe I'm just heartless thanks to ag school...I found them unconvincing, but for many people sentiment and bonds with animals have a lot of weight.

I agree with others here that the Paleo Diet concept just makes sense to me on a common sense level. If anatomically modern humans appeared about 200,000 years ago, then paleo is clearly what they were eating. The exact menu may have varied from season to season and biome to biome, but clearly they were eating foods found in their local environment. The archeological evidence is pretty compelling that paleolithic humans were hunting and fishing. Studies of contemporary hunter/gatherers show that animal protein is a prized food source. If this diet was so bad for humans to eat, how did we avoid extinction?

If this is how we've been eating for 200,000 years (and 2 million years before that as proto humans), I think the burden of proof must be borne primarily by the other side, especially after the lipid hypothesis seems to have fallen down. Moreover, we were told in 1982 to reduce saturated fats in our diets and to make up the caloric difference with "low fat healthy grains." That didn't work out either. Even as our society (in the aggregate) derives fewer of our calories from saturated fat, the incidence (again, in the aggregate) of obesity, heart disease, and metabolic symdrome generally, are up, way up.

Science is a process, and often messy. I think the truth will shake itself out eventually, but for now I'll eat paleo. There is now so much conflicting information out there about diet, even among those with the right degrees, that I don't have much choice--I gotta eat something.

One of the common arguments I tend to hear against paleo is that 10,000 years IS enough time to begin evolving to support grains. Evolution is not a light-switch. Things happen gradually. We were all originally lactose intolerant, you know. We've phased that out (largely) in the same time span, so why can't we also apply that to grains?

I'm not saying I agree, but I do not believe that "grains are the devil". I think that high carbohydrates are terribad, and grains give you a big carbohydrate punch in the mouth

An argument against Paleo from a practical perspective is that 6.5 billion people are not able to be fed on such a diet, at least not if each person is eating a good amount of meat. This would be a good reason for the government to advocate a largely grain based diet. As long as most people can still live a pretty good, long life things are okay. So what if they need some modern medical interventions along the way. However, this reasoning shouldn't preclude an individual from eating Paleo if it's within their means.