Corn, a familiar food staple worldwide, looks very different today than it did thousands of years ago. Its plump, sweet kernels arranged neatly on a large cob are a product of extensive transformation. To understand this transformation, one must look back at its earliest form, a wild plant unlike modern corn.
The Original Plant
The wild ancestor of modern corn is a grass known as teosinte, which originated in southern Mexico. This plant was characterized by multiple stalks and a bushy appearance, unlike the single, tall stalk of today’s corn.
Instead of large ears, teosinte produced small, slender spikes, two to three inches long. These spikes contained a limited number of seeds, between three and twelve, arranged in a single row. Each of these small, triangular kernels was encased in a tough, stone-like shell. The kernels were attached to a thin central axis, lacking the thick cob structure.
How Corn Transformed
The transformation of teosinte into corn began approximately 9,000 to 10,000 years ago in the Balsas Valley of southern Mexico. Early Mesoamerican farmers played a significant role by selectively cultivating plants that exhibited desirable traits. This process involved choosing seeds from plants with slightly larger or softer kernels and replanting them for the next harvest. Over many generations, this careful selection gradually altered the plant’s characteristics.
A single gene, teosinte branched1 (tb1), was influential in this change. The tb1 gene represses the growth of side branches, leading to a more centralized stalk. This genetic shift was central to changing teosinte’s bushy architecture into a single-stalked plant. The selection for specific alleles of the tb1 gene contributed to both reduced branching and increased ear size. Furthermore, a genetic mutation caused the hard outer casing of the teosinte kernels to disappear.
From Ancient Grain to Modern Crop
The earliest domesticated corn, while a step beyond teosinte, still differed from today’s varieties. These ancient corn ears were small, around two inches long, and contained only a few kernels, lacking a developed cob. The kernels, though no longer fully encased, were smaller and harder than modern kernels, often retaining partial coverings. Archaeological findings show cobs with as few as two rows of kernels, though later examples from around 4,000 years ago had 12 to 14 rows.
Through continued selective breeding by human farmers over thousands of years, corn underwent further development. This ongoing process resulted in the large, soft-kerneled ears found today, which can grow up to 12 inches in length and contain hundreds of exposed kernels. The development of hybrid corn in the early 1900s also played a role in increasing yields and shaping the crop. This long history of human intervention, guided by careful observation and selection, transformed a wild grass into one of the world’s most widely cultivated and recognizable crops.