This is One Corny Post: The Domestication of Maize (Corn)

 

Figure 1: Comparison of teosinte and modern corn (Image Source: Nicole Fuller, National Science Foundation)

Corn is a very versatile crop used in various food products (e.g. flower, starch, syrup, etc.), ethanol (fuel), livestock feed, and even, in some cases, plastic production.  Thousands of varieties of corn are grown across the globe, thereby making it a primary cash crop and source of income for people everywhere.  It is also a staple of many people’s diets, making it a great and necessary nutritional resource, too.  What you may not know is that corn is also a great example of artificial selection, which refers to situations were organisms are intentionally bred for desired characteristics.  Today’s blog post will explore the origins of corn, and why it is important to understand its evolution.

 

Corn, or more commonly referred to as maize in the archaeological literature, is not a naturally occurring product in the environment.  It was actually derived from a plant known as teosinte (Figure 1).  Teosinte is a natural grass common throughout the Americas, and it produces a fruit that has a very small, slender cob and thick, almost impenetrable husk.  There are many variations within the teosinte plant species, which made it a perfect plant to work with among early human agriculturalists.  It is unclear what specifically led these individuals to artificially select and breed specific teosinte plants, but their work, which began almost 9000 years ago in southern Mexico, paid off.  They turned this unappetizing plant into a dietary staple not just for peoples of the Americas but the world.

 

Figure 2: Examples of Various Types of Corn (Image Source: Popcorn.com)

Archaeologists were able to track the evolution of teosinte into modern day corn through various archaeological discoveries throughout Central and South America.  Early evidence noted specific changes in size and shape of early teosinte plants found in refuse spots (i.e. middens or trash heaps), along with evidence of consumption of the kernels.  Over time and with the advancement of paleogenetic work scholars were able to track the molecular evolution of this plant.  This led to a more recent and revolutionizing discovery, which showed that corn underwent several evolutions.  The first began in Mexico, and then subsequent domestication and evolution events occurred 6500 years ago in the western Amazon region.  Peri-domesticated corn was either sent or brought to the region and adopted into the agricultural exploits of the region.  The corn grown here was actually domesticated before the corn in its place of origin in Mexico, which accounts for the various types of corn that exists today (Figure 2). 

 

This information not only provides us insights into the artificial selection patterns and evolution of corn but also into the prehistory of human populations of South America.  Archaeological evidence demonstrates that whenever corn started being grown in a region it was the direct result of human migration to the area.  Corn is very dependent on humans to grow it, care for it, and harvest it, which is also very important in understanding how to maintain it in rapidly changing environments that exist today.  By understanding the human relationship with the evolution of corn one can better comprehend and initiate future changes in various other staple crops, which could help prevent crop loss, extinction, and food shortages.

 

Bibliography

Bower, B. (2018, December 13). Corn domestication took some unexpected twists and turns. Science News.

Katz, B. (2018, December 14). Rethinking the Corny History of Maize. Smithsonian Magazine.

Mangelsdorf, P. C., MacNeish, R. S., & Galinat, W. C. (1964, February 7). Domestication of Corn. Science Magazine, pp. 538-545.

Smithsonian. (2018, December 13). Scientists overhaul corn domestication story with multidisciplinary analysis. Retrieved from Phys.org: https://phys.org/news/2018-12-scientists-overhaul-corn-domestication-story.html

Tian, F., Stevens, N. M., & Buckler IV, E. S. (2009). Tracking Footprints of Maize Domestication and Evidence for a Massive Selective Sweep on Chromosome 10. National Academy of Sciences.