Some interesting snippets from http://www.answers.com/topic/the-nat...story-of-wheat

Keep in mind that PD was first unequivocally described in London 1817.

All plants are identified by their chromosomes. Every variety of wheat grown today has arisen from wild, fourteen-chromosome wheat, undoubtedly einkorn. Einkorn and fourteen-chromosome wild grass crosses created twenty-eight-chromosome (tetraploid) wheats. Only one twenty-eight-chromosome species can be found in nature: wild emmer (T. dicoccoides).

Modern bread wheat varieties have forty-two chromosomes and evolved from crosses between emmer and goat grass, which is the source of the unique glutenin genes that give bread dough the ability to form gluten.

Three major advances were vital in the expansion and development of wheat production and consumption. First, in the early 1800s,.....

For thousands of years, all wheat, regardless of variety, was grown, harvested, and co-mingled in storage. As milling and the wheat food industry became increasingly sophisticated, companies became aware of the uniqueness and importance of wheat varieties.....

Tenant farmers were compelled to mill their grain at their landlord's mill, and a "soke" of one-sixteenth of the production was kept by the landlord. Until the soke system died out in 1791, wheat was not sold much beyond the landlord's domain....

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From all this it seems that there is a wide range of wheat varieties with major differences at the molecular level. That the grains implicated in celiac disease share goat grass ancestry and are recent arrivals. That things changed with the Industrial Revolution and wheat went from a regionalized mix of different varieties to a more specialized single variety type of use. A generation later, James Parkinson wrote his pamphlet.