The Americas

Dolores Piperno, an archaeologist, at the Smithsonian Tropical Research Institute, investigated the domestication of corn from teosinte in the Balsas Valley of Mexico. [1] Early plant grinding stones were found in layers with charcoal from fires, which were dated at 8,700 years old. If not for the exploding husk in the process of making popcorn, corn would never have begun the long genetic journey from teosinte (Figure 14-44). After domestication, corn became the largest part of the Mesoamerican diet. The energy that it provided played a key role in the development of the Mayan, Aztec, and Incan civilizations in Central and South America. It became popular in Europe after Christopher Columbus brought it back from his journeys to the Americas.

Studies of corn genetics show that changes in only a few genes have resulted in dramatic changes in the plant. In the 1930s, George Beadle investigated how many genes controlled the differences between teosinte and maize (corn) by breeding 50,000 plants and found that 1 in 500 plants looked like maize and 1 in 500 plants looked like teosinte. This meant that only 4 or 5 genes controlled the difference between corn and teosinte. John Dobley’s lab at the University of Wisconsin found that a single gene controls the husk formation over the kernel. The lab also found that another gene, called the branching gene, caused the single stalk to form rather than the bushy teosinte plant. Both of these genes were regulatory genes, which control the activity of other genes.

Corn was the basis of Mayan, Aztec, and the other great civilizations of Mesoamerica. It became an important part of the art, culture, and religions of these societies. Another important food in Mexico was the tomato. It was originally from South America, but it seems to have been domesticated by 500 BC in Mexico.