The First Milpa - Jared Diamond, Corn, and Mexico

Jared Diamond identifies at least five locations around the world as independently domesticating plants - including Southwest Asia, China, Mesoamerica, Andes upland and Amazon foothills, and the latest chronologically, the Eastern United States. The first four became sites of early advanced civilizations. The first of these was Southwest Asia, about 8500 BC, followed by China, in 7500 BC.

In Mesoamerica, it is the story of corn. Corn, or maize, and the corn field, milpa, are sacred in Mexico and Central America. The holy book, Popol Vuh, talks about the flesh of the first father and first mother being made from corn mush. For decades historians and scientists have debated the origin of corn. Now, thanks to advances in molecular biology and genetics, we are much closer to the answer: teosinte grass from Mexico.

There are two big surprises to the news announced in March 2009 - first, it was not just any teosinte, but Balsas teosinte, or Zea mays parviglumis. Surprisingly it was found in southwest Mexico in mid-level elevations, along the Balsas River which borders Guerrero, Michoacan, and Jalisco. Teosinte is a wild grass that has edible grains - a small, hard grain that must be smashed open with a rock. Guatemalan teosinte, or Zea luxurians, with optimal conditions in the highlands of Guatemala, northern El Salvador, and southern Honduras. But Balsas teosinte has optimal growing conditions in western Mexico.

The second surprise was the date - the site shows that corn was domesticated by at least 6700 BC, along with squash. The practice of cultivating corn spread quickly south - by 5500 BC to Panama and soon thereafter to Columbia and Ecuador. It made the move to the north, out of the sub-tropics, much more slowly, arriving in the southwestern US by 0 BC and to the Mississippi Valley by 1000 AD. By at least 3000 BC, beans (cooking beans) were also domesticated, and together with corn create a complete protein.

While squash and corn, and later beans, made their way south, at least three domesticated plants from South America made their way north: yuca (manioc), peanuts, and cacao.

It is at least worth mentioning that temperatures were slowing rising at 6700 BC, entering the warm period called the Holocene Climate Optimum. Temperatures rose much more dramatically in northern latitudes, but there was likely mild warming in the sub-tropics. The previous ice age had ended by at least 9000 BC, but it seems likely that from 9000 to 6700 BC, the range of Balsas teosinte was slowly drifting northwest from Central America toward the Guerrero-Jalisco coast. Since scientists did not find corn and teosinte together at the 6700 BC site, it is possible that corn actually was hybridized even earlier and that this hybridization could have happened further south along the Guatemala or El Salvador coast. There are hints that this might be true, but I save that for a later post.

Jared Diamond says that corn was very hard to domesticate from teosinte, leading to a 5,000 year head start for Southwest Asian cultures. He did not have the benefit of the 2009 announcement mentioned above, which proved a much earlier date. In fact, Mesoamericans were less than 2,000 years behind in plant domestication. It is true that it likely took several thousand years of hybridization to grow corn that produced thumb size cobs to corn that produced finger size cobs. Yet, there was another, more serious problem with corn that kept it from being the generator of advanced culture. When the Mayans of the Guatemalan/Salvadoran Pacific Coast solved this problem in about 1500 BC, civilization took off like wild fire in Mesoamerica. Any guesses? Next time...

[Post Script: I now believe that the hybridization process may have begun as early as 8300 BC and took place in El Salvador at the close of the last Ice Age. Feb. 25, 2010]

Comments

[rolando vela]

For me, corn are really the best cereal. He come from the care and technique of our people.
Tomorrow. I will going to north of El Salvador, in San Ignacio, Chalatenango.
On the road to canton Las pilas, in the border, exist a caserio Teosinte. I dont now since when is named there.

[Web Development Karachi]

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