How Did Corn Grow Corn?

Corn, potatoes, and chocolate are all important crops that originated in Latin America. These crops spread throughout the world and are important economically and for use as food. How domestic corn was developed
Corn was derived from its ancestor teosinte, a wild grass which grows in parts of Central America and Mexico. Teosinte is different than corn in a number of ways. It does not grow on a large leaf covered cob, thus allowing it to break off the plant and spread more effectively and has a hard shell. Its color is similar to many rocks which decreases the chance of being eaten, unlike corn. There are six species of Teosinte: Zea mays ssp. huehuetenangensis which grows near the border of Chiapas, Mexico; Zea mays ssp. mexicana which grows

The only evidence of early corn in Northern Mexico is in Tamaulipas in Northeastern Mexico. However, the early corn grown in Northeastern Mexico and Southwestern America are genetically different and show that they developed at approximately the same time. There are two major theories as to how corn started being grown in the American Southwest. One theory proposes that the knowledge of how to grow corn was spread by groups of foraging people. The other theory proposes that migrating farmers spread the knowledge. The theory that foragers spread the knowledge of corn growth has usually been more accepted; however, since 2000, the theory that migrating farmers spread the knowledge has been gaining acceptance. This theory suggests that domestic corn spread from Northwestern Mexico to Southwestern America when farmers moved north to obtain fertile land. There are a few areas in the southwestern United States that contain evidence of historical corn growth; these sites were in Arizona and New Mexico. The sites were Old Corn, McEuen Cave, Clearwater, Las Capas, and Three Fir Shelter. Old Corn is on the Colorado Plateau in western New Mexico, McEuen Cave is in the Gila Mountains in Eastern Arizona, Clearwater and Las Tapas exist in the Tucson Basin in Southern Arizona, and Three Fir Shelter is located on the Colorado Plateau in Northeastern Arizona. (Figure 2)

http://www.pnas.org/content/106/50/21019.full

These sites are geographically diverse and show the adaptability of corn in the American southwest, but more research needs done on the early history of corn in order to determine how corn diffused from Mexico to North America as there is little substantial evidence indicating how corn spread at this point.