Read an Academic Passage

[1]Maize, or corn, is one of the world's most important crops, yet its wild ancestor looks very little like it. That ancestor, a grass called teosinte that still grows in Mexico, produces small ears with only a few hard-shelled kernels. For many years, some scientists doubted that such a plant could have given rise to maize.

[2]Genetic studies have settled the question. They show that maize was domesticated from teosinte in the Balsas River valley of southern Mexico roughly 9,000 years ago. Early farmers did this without any knowledge of genetics. Each season they saved seeds from the plants they preferred, such as those with softer kernels or ears that did not fall apart, and planted them the following year. Over thousands of generations, these small choices transformed the plant.

[3]The process also made maize dependent on people. A modern ear holds its kernels tightly inside a husk, so the seeds cannot scatter on their own. Without farmers to remove and plant the kernels, maize would disappear within a few seasons. In this sense, domestication changed both partners: humans came to depend on maize for food, and maize came to depend on humans to reproduce.