Corn, a widespread crop today, looks dramatically different from its wild ancestor. It has undergone an extensive transformation over thousands of years, evolving from a humble grass into the large, kernel-filled ears recognized globally. The story of this profound change was shaped by natural processes and deliberate human intervention over a long period.
The Original Plant
The wild ancestor of modern corn is a grass called teosinte, primarily found in southern Mexico and Central America. Teosinte plants are bushy, characterized by multiple short, branching stalks several feet tall. Instead of a single, large ear, teosinte produces small spikes, typically only a few inches long, each containing a limited number of seeds. These seeds are triangular, hard, and encased in a tough, acorn-like fruitcase, which protects them. Teosinte thrives in diverse environments, from moist areas along streams and hillsides to disturbed ground and agricultural fields.
From Wild Grass to Early Crop
The transformation of teosinte into early corn began around 9,000 years ago in Mesoamerica, specifically in the Balsas Valley of southern Mexico. Early human farmers initiated this change through a process known as selective breeding. They chose seeds from teosinte plants with desirable characteristics, such as larger kernels or softer shells, for replanting. This methodical selection over many generations gradually altered the plant’s traits, steering its evolution towards a more domesticated form. The shift was not sudden but a slow accumulation of changes, driven by human preference for traits that made the plant more useful and easier to cultivate.
Key Evolutionary Changes
During domestication, corn underwent several distinct physical changes that set it apart from teosinte. A key change involved the plant’s architecture, moving from bushy, multi-stalked teosinte to a single, unbranched stalk. The small, hard teosinte seeds, protected by a tough fruitcase, evolved into much larger, softer kernels, losing their tough casing for easier consumption. The small, few-seeded spikes of teosinte developed into a single, prominent cob, holding hundreds of kernels in multiple rows and covered by protective husks. These modifications, partly influenced by genes like teosinte branched1 (tb1), made corn a more efficient food source, increasing yield and easing harvesting.
The Diversity of Modern Corn
The evolutionary journey of corn continued long after its initial domestication, leading to the wide variety seen today. Modern corn encompasses several types, each adapted for specific uses and environments. Dent corn, also known as field corn, is the most common type, primarily used for livestock feed and industrial products, characterized by a small dent in its mature kernels. Sweet corn is harvested young for its high sugar content and tender kernels. Other types include flint corn, often used for cornmeal or decorative purposes (with popcorn being a specialized type), and flour corn, easily ground into flour due to its soft, starchy interior. These diverse forms result from ongoing selective breeding, adapting corn to various climates, soil conditions, and human needs.