Now we have all learned that grains might not be a good source for energy and that it causes inflammation in the body and fat storage, in some cases obesity.
Why does not all people eating grains at a regular basis get cancer/get sick/get fat? I can easily say that I am the most "pure" paleo/primal eater in my group of friends/family/work colleagues (roughly 150 people, various ages). No one of them are primal and all eat grains as a staple food.
If grains are so bad, why has the human as a species evolved a digestive system which can handle them? IF we were not able to handle them them we would not eat them (as such, the "caveman did not eat grains and we have not yet adopted during the approx. 15.000 years we have been eating grains so it is bad for us" theory falls. We do not eat the nut of the pinecone since we can not handle them.