Our bodies contain the same DNA as our ancestors from 6-10,000 years ago. Grains were introduced ~ 5-6,000 years ago. Hybridization has altered grains such as wheat, rye, spelt, barley. We do not have the DNA to break these grains down in our intestinal tracts.
Europeans discovered that when they used a 'sour' starter culture, which broke down the gluten, then they were able to consume the bread w/o gastro-distress. Dough starters actually increased in potency over time, as family recipes we