Gene Logsdon, the Contrary Farmer, has an interesting post up on the correlation between the downfall of societies and corn.

From the post:

~~~~~

In Mayan culture and in the Late Prehistoric Age of the mound-building American Indians, corn was the major crop. It’s what they mostly ate. Archeologists are finding evidence that this diet led to deteriorating health and maybe was the main reason the mound-building Indians seemed to mysteriously disappear about a thousand years ago. The collapse of the mound-building culture and the collapse of the Mayan civilization earlier coincided with an agriculture and diet dominated by corn. In both cases, rising population and diminishing soil fertility encouraged war and instability because the only way the people knew to maintain high corn yields was to find new land to grow it on.

~~~~~~~~~~~~

Perhaps celiac disease developed in the corn-centered diet and the continual eating of corn further inflamed their guts to the point of death?  Or to the point of inability of the gut to digest food properly, and they died of malnutrition and disease due to their gut being unable to mount an attack when a pathogen appeared?

The more I read of farming, the more convinced I am that diverse farms are the answer to soil depletion of nutrients and beneficial organisms; to fight off harmful insects (or at least keep them in check).  I was just reading about planting beets yesterday, and they recommended not planting them in the same spot year after year.  The mistake that most beginner gardeners make is thinking that since a plant did so well in one spot, that they should plant the same plant there again the next year.  Nope.  They were saying that beets are “heavy eaters” in that they take up a lot of nutrients, therefore one needs to plant something else the next year to put nutrients back into the soil.  This also goes along with composting food scraps, leaves, twigs, and dirt, because they also put nutrients back into the soil.