The argument re grains isn't "don't eat anything that would need to be processed" ... the argument is "don't eat grains because some of their anti-nutrients aren't neutralized by cooking or processing."

I don't see the correlation between the following:

Tubers - Cook and eat.

Grains - Thresh, sprout, separate remaining husk and bran from endosperm via industrial grinding (not done with teff due to it's size), soak, dry, bleach (optional), process to powder or steel cut, reconstitute with liquid, cook, eat.

The concept of "don't eat anything that would need to be processed" is a good "Golden Rule" for newbies, but specifically eating a paleo diet would align more with "Don't eat what your ancestors would not have been able to eat". There is evidence of cooked food by sapiens ancestors beyond 1mya. I would like to think that qualifies.

Kurt Harris had a rant about the processed = bad idea that I'm not finding now so I'm going to have to paraphrase.

Processing, in and of itself, is not a bad thing. It's how we get cream from milk, butter from cream, yogurt or kefir from milk, etc. Fermented vegetables? Processed. Dry-aged meat? Processed. Rendered tallow/lard? Processed.

What you need to consider is what is added, what is taken away, and what is changed. When you process corn to get corn oil you are concentrating the oil, something that corn does not have a lot of in the first place. Now you have an evolutionarily novel amount of something we can safely consume.... in small amounts. When you cook a tuber or vegetable the plant's cell walls burst, releasing the starches, sugars, and other nutrients. We need fire for this because cellulose is indigestible to humans.

The problem with grains is not the amount of processing that's necessary to make them edible, it's that they are more toxic than most other edible plants. By the way, cassava, one of the "safe starches", can induce cyanide toxicity if not properly prepared. But if you follow what needs to be done, it becomes safe and non-toxic to consume. Gluten proteins are very difficult to digest, and I don't know how much of this is fixed by following traditional preparation methods (sourdough fermenting). Non-gluten grains are easier -- brown rice can simply be polished to be in the clear, others might need some soaking, sprouting, or fermenting.

Beth has it right. We have to remember why we're doing this in the first place. It isn't simply a matter of "eat what our ancestors ate and that's that", because none of the foods that were around back then are still here now. Or at least not in the same form. We are using their diet as a basis for creating hypotheses to see what works for us, and what doesn't. I often use the example of olive oil, which IS a neolithic food that we can handle quite well.

Grains aren't bad for us because our ancestors didn't eat them. That argument makes no sense. They're bad for us because we see again and again the fact that they are a gut-irritant and wreck havoc in our bodies. Paleo is a science-based methodology basing it's hypotheses off of evolutionary biology.