Corn, known globally as maize, stands as one of humanity’s most significant crops, providing a substantial portion of the calories consumed by humans and livestock alike. The journey of this familiar grain from its wild origins to its current form has long fascinated scientists, offering insights into the ingenuity of early human societies.
The Wild Ancestor
Modern corn descended from a wild grass called teosinte, which looks very different from the corn we recognize today. Teosinte is a tall, branching plant with multiple stalks, and its kernels are encased in a tough, hard fruitcase, making them difficult to eat. Unlike the large cobs of modern corn, teosinte produces small ears with only a few kernels arranged in a single row.
Though initial visual differences led to skepticism, extensive genetic and morphological studies have since confirmed teosinte as the direct ancestor of maize. Early humans began the process of transforming this wild grass into the versatile crop it is today.
The Cradle of Domestication
The domestication of corn occurred in the Balsas River Valley, located in southwestern Mexico. This region’s geographical and ecological characteristics provided an ideal environment for this agricultural revolution. The valley, characterized by a lowland seasonal forest, supported the growth of Balsas teosinte, the specific subspecies identified as maize’s closest wild relative.
The Balsas River Valley is rich in genetic diversity for teosinte. Archaeological evidence and scientific analysis pinpoint the approximate timeframe for corn’s domestication in this area to around 9,000 years ago.
Scientific Evidence of Origin
Scientists have pieced together corn’s origin through various lines of evidence, such as archaeological discoveries and genetic analysis. Archaeological digs have unearthed ancient corn cobs and pollen grains, providing a timeline for its early development. For instance, at Guilá Naquitz Cave in Oaxaca, Mexico, maize cobs dating back approximately 6,250 years ago represent some of the earliest macrofossil evidence of domesticated maize in the Americas. These early cobs show features indicating an ongoing domestication process, such as a non-disarticulating rachis, meaning the kernels remained attached to the cob.
Genetic studies support the connection between teosinte and modern corn. DNA analysis of modern corn and teosinte populations reveals their close genetic relationship and confirms a single domestication event in southern Mexico. Researchers have identified specific genes responsible for the differences between teosinte and maize, such as teosinte glume architecture1 (tga1). A single amino acid substitution in the tga1 gene in maize, compared to teosinte, significantly reduced the tough casing around the kernels, leading to the “naked” kernels characteristic of corn. This genetic change transformed the TGA1 protein into a repressor, altering how it regulated kernel development and making the kernels easily accessible.
Global Spread of Maize
Following its domestication in the Balsas River Valley, maize spread throughout the Americas. It moved southward into Central and South America and northward into what is now the United States. Indigenous cultures across these continents adopted maize, integrating it into their agricultural systems and diets.
This widespread adoption played a significant role in the development of complex societies in the Americas. By the time Europeans arrived, maize was a major food source across the continent. After European contact, maize spread globally, transforming agriculture and diets worldwide, solidifying its status as a staple crop.