We missed the evolution
The hunter-gatherer diet of our ancestors was high in meat and poultry, including the fat and edible organs. In addition, when fruit was in season it was probably eaten in abundance and preserved by drying the fruit in the sun. They probably also ate some leaves, nuts, roots and grains but in low quantities because of the labour needed to gather them in the wild. The wild ancestors of many of our vegetables and legumes were inedible and some were unsafe to eat because they were toxic.
When our ancestors figured out how to cultivate crops in abundance, to cultivate vegetables to be edible and less toxic, and to domesticate animals for food, they settled down and significantly changed the balance of their diet from one that was high in animal protein and fat to one that is high in starch and included many more legumes and vegetables. Their digestive systems evolved to handle the different diet – imperfectly – no one today can digest all starch, legumes and vegetables in a typical diet but most people do not suffer diarrhea from eating these foods.
I do not know how my ancestors missed the evolution despite living for millennia in agricultural settings. Food intolerance appears to be a problem of an unevolved or de-evolved digestive system.
When our ancestors figured out how to cultivate crops in abundance, to cultivate vegetables to be edible and less toxic, and to domesticate animals for food, they settled down and significantly changed the balance of their diet from one that was high in animal protein and fat to one that is high in starch and included many more legumes and vegetables. Their digestive systems evolved to handle the different diet – imperfectly – no one today can digest all starch, legumes and vegetables in a typical diet but most people do not suffer diarrhea from eating these foods.
I do not know how my ancestors missed the evolution despite living for millennia in agricultural settings. Food intolerance appears to be a problem of an unevolved or de-evolved digestive system.