Americans have a particularly sterile gut, not enough bacteria.
And no, we have not been eating Gluten since the beginning of time, humans didn't evolve eating grains, especially highly processed grains. I have Celliac-like symptoms but don't have Celliac, If I eat too much wheat my abdomen blows up like a balloon and stays like that for days. Gluten-Free has a fad aspect to it, but even ppl like me without Celliac can't be eating a lot of grains.
A good rule to follow is don't eat food sold in boxes.
And don't start with the anti GMO stuff, if you do, you have no idea what a GMO is... https://www.youtube.com/watch?v=1ecT2CaL7NA Anti GMO is like being part of a religious cult, or just really stupid.