TEPIC, MEXICO—At a site in the mountains of western Mexico known as “The Ledge of the Souls,” archaeologist Mauricio Garduño recently discovered a complex panel of pictographs dating between 850 and 1350 A.D. Carved in the pictorial tradition of the Aztlan culture, the panels are divided into two styles. “In the eastern half we found designs related to fertility-fecundity: rain clouds, sectioned snail shells, and feminine vulvae; in the western half, we found cranium profiles whose front point to the east, precisely towards the sunrise.” Garduño thinks some of the panels may have played an astronomical role in the Aztlan annual ritual cycle.