Dr. Ben has said:

> Grain related illnesses are not a great problem for people who start
> reproducing at 14 and have a life expectancy of 25-35 years.

It would seem to me infants born with a high degree of sensitivity to
grains and agricultural products would have a greater chance of dying
during early childhood and therefore would not reach the age of
reproduction in as great of numbers as those infants that can tolerate
those products well. It would become a form of natural selection. Those
who can tolerate and do well on the diets of the culture they are born
into survive and reproduce. Of course, not all of those who are
insensitive die, maybe even most of them reproduce, but over a period of
time there would be a gradual shift in genetic makeup of the population
due to this natural selection pressure.

Tom