This article confronts the cultural limitation of critical race work in the United States by examining genomic practices at two national institutes in Mexico—one focused on people and aimed at sampling “the Mexican genome,” the other focused on plant biodiversity and “razas de maíz” or races of corn. The human genome project emphasizes admixture in ways that seem to confound claims about the racialization of genomics research in the United States; the biodiversity project highlights the broad extent to which “race” is also about nonhumans. Taken together, these projects suggest a greater breadth and depth to racial thinking than is typically considered in U.S.-based accounts. Grasping this wider scope to race involves, first, foregoing a strict delineation of the social and the biological and, secondly, recognizing that uses of race on nonhumans indicate that racial thinking entails profound questions concerning the nature of species. “Razas de maíz” suggest that racial thinking is both older and more deeply engrained than the modern forms with which we have been most concerned; it may well derive from processes of domestication that are quite ancient and encompass a range of contradictory, complex ideas and practices concerning the relations of humans and nonhumans.