Figure 2.

Maize dispersion and diversity. Maize originated in the Balsas river basin of southwestern Mexico approximately 9000 years ago (Matsuoka et al., 2002). Over the next several thousand years, it spread through the Americas, crossing (and adapting to) deserts, mountains, tropics and almost every other environment present across both continents before contact with European explorers spread it throughout the world. Arrows show probable routes of pre-Columbian dispersion based on phylogenetic reconstruction (Matsuoka et al., 2002); biome data are from the USDA National Resource Conservation Service (http://www.nrcs.usda.gov).