We drove to the St. Louis area specifically to check out Cahokia, the site of the largest pre-Colombian urban area north of the great Aztec, Mayan and Zapotec cities in what is now Mexico. At one point in the 13th century, the larger "metro" area of this Mississippian civic complex had about 20K inhabitants, big or bigger than then-contemporary Paris and London.
Unlike the pyramid structures of Tenochtitlan or Chichen Itza, the residents of Cahokia built their huge structures of earth rather than rock. Their "mounds" are reminiscent of the slope-panel structures of Monte Alban, but bigger. Overall, Cahokia is an awe-inspiring place, and like all ruins of great civilizations, both magnificent and sad.
No one knows why Cahokia was abandoned. One possible reason that we overheard a park guide suggest is that they ran out of food, which is one of several speculative reasons given for the abandonment of the great Mayan cities. Like those cities, Cahokia was abandoned long before Europeans arrived with their highly developed diseases, which were largely responsible for eradicating native populations throughout the Americas.
The lack of food, however, seems an odd and inexplicable reason for Cahokia's demise. The Mississippi river runs within eye-shot of the ancient city, and there must have been a lot of fish in there. The woods were full of venison and birds (though it seems, based on the few remaining pieces of physical culture, that these people held birds in particularly high regard, so maybe they didn't eat them).
There was also a lot of stuff growing wild (nuts, berries, lamb's quarters) and some cultivated crops, including squash and corn. And that's where things get weird.
Corn likely originated in Central Mexico, and it's presence in our part of the world suggests there was commerce between Mexico and the Mississippians, who could have traveled down the river to the Gulf. Sea shells in some graves indicates they made it down to the ocean, which isn't at all surprising, and it was probably on trips down there that they brought back corn.
"But they didn't have beans?," The Wife wondered.
It is odd. The Three Sisters – squash, corn, and beans – grew and grow all over Mexico, and they work well together, complementing each other in so many ways. The beans fix nitrogen in the soil; corn uses that nitrogen, and the beans twine up the corn stalks, while the squash creates natural mulch and holds the moisture in with their big leaves. These vegetables seem made for one another, and they also complement one another nutritionally.
Corn by itself is actually not such a wonderful food source, as eating it in the absence of other foods can lead to pellagra,
So why did this Mississippian civilization, which was so advanced in so many ways, have no beans? Even if the lack of food was not the main reason for their abandonment of their city, it's just darn odd that the people who built this great city didn't have beans, which seem an almost unavoidable crop and are enjoyed everywhere in the world.
Unless they just didn't like beans…which is also unthinkable.