The Sonoran Desert has its deep origins in the desert valleys of southern Mexico. We visit two such valleys—the Valley of Cuicatlán in Oaxaca, which connects with the Valley of Tehuacán in Puebla —as we trace the ancient roots of the vegetation of the Sonoran Desert. These valleys have been home to native peoples for many thousands of years. Part of the valleys’ lure is the archaeological sites that date as far back as 300 years before the Common Era. Under the guidance of our three experts, the trek takes us through rural towns and villages, biological reserves, cathedrals, regional markets, archaeological sites, and museums.