Why haven’t humans evolved beyond gluten sensitivity?

I’ve done a lot of reading about gluten sensitivity, and because there’s so much research and data on both sides of the gluten is ok/gluten is the devil fence, it seems to me I just need to go with my gut (pun intended) and believe the research that seems more legit to me. Therefore, I have limited my gluten intake for about 2 years now, and while I haven’t been perfectly gluten-free, I have gone for short stints with no gluten, and I honestly don’t think I am gluten-sensitive. I still see, from a logical if not physical perspective, the benefits of avoiding gluten, so I still avoid it, much to the irritation of my spouse. His argument has repeatedly been, “If gluten is a real problem, why haven’t humans evolved to process gluten properly?” I have not been able to answer that question to my satisfaction, so here we are.

This article from Doctor Auer gives a quick history of grains in human diets, from ancient Egypt to present day, possibly correlating with the rise of osteoporosis, diabetes, and later cancer and various degenerative diseases. Modern production methods strip out most of the grains’ nutrients, add chemicals, and leave behind naturally occurring toxins that cause gut inflammation. To sum up:

We must remember that evolutionarily speaking, we have been around for almost two million years, but we have only been eating grains for a few thousand. As such, our bodies have not had the time to adapt to this “new” food in our diet. Furthermore, modern farming, harvesting, and processing methods have stripped grains of their nutritional integrity, decreasing their digestibility, and making them highly toxic and inflammatory food to our bodies.

Here’s more, from Science 2.0:

“Only for the past ten thousand years have we had wheat-based foods in our diets, which in evolutionary terms makes wheat almost a novel food. If you put that in context to the 2.5 millions years that mankind has been on earth, it makes sense that our bodies are still adapting to this food, and more specifically, the gluten that it contains.”

But the best answers come from this Paleo Mom article. She explains the role of evolutionary pressure, or factors that reduce reproductive success, in adaptation, and states that while humans have had enough time to adapt to grains, there has not been sufficient evolutionary pressure to do so, because health issues related to grain consumption do not generally affect reproduction rates. (There’s an interesting reader comment at the bottom about gut flora that’s worth researching, but not for this post.)

So the answer I will give to Spouse and anyone else is: Humans are adapting to process grains, but have not yet fully adapted because eating grains does not interfere with reproduction enough to select out grain-intolerant genes at a high rate.