At roughly the same time that Asians began experimenting with domesticated wheat, Indians in south central Mexico began growing teosinte, a type of grass. Over the next several millennia teosinte began to evolve into a plant similar to modern corn. The breeding experiments led to testing other strands and seeds as well as the development of chili peppers, avocados, cotton, and other plants. For North American Indians, however, corn, beans, and squash were by far the most important native cultigens. Because women were the primary farmers in prehistoric North America, the plants were always associated with the feminine powers of fertility. In fact, the Iroquois called them the "Three Sisters." Squash was the first of the Mesoamerican crops to infiltrate North America, and by 1000 B.C. the plant had reached the East. Also known as cucurbits, the squashes were similar to present-day pumpkins...