The seeds of most are edible, although some are infected with endophytes and fungi. Pseudocereals are non-grasses that produce similar fruits or seeds. Grain amaranth and buckwheat are examples. The world's major grains are listed on pg. The major producing countries are listed on pg.
Populations are variable.
They are stable only for a given situation. A change in selection pressure will cause a change in the genetics of the plant involved. Domestication is an evolutionary process under the influence of man. Usually a slow process. As long as gatherers only gather, they exert little selective pressure.