In 1600 they were the largest, most technologically advanced indigenous group in northwest Mexico, but today, though their descendants presumably live on in Sonora, almost no one claims descent from the Ópatas. The Ópatas seem to have "disappeared" as an ethnic group, their languages forgotten except for the names of the towns, plants, and geography of the Opatería, where they lived. Why did the Ópatas disappear from the historical record while their...