A reanalysis of population dynamics in the Casas Grandes region of Northern Mexico using mitochondrial DNA

The Casas Grandes region in northwest Chihuahua, Mexico, is ideally situated to explore the notion of contact between the US Southwest/Northwest Mexico and Mesoamerica, as it lies geographically in a region where cultural traditions were combined in unique ways. In order to explain these dynamics, past researchers have suggested that the primary catalyst for the flourishing Casas Grandes population in the thirteenth century A.D. was caused by migrants from Mesoamerica or from larger populations to the north. We analyzed mitochondrial genetic data from individuals interred at sites that date to earlier (A.D. 700–1200) and later (A.D. 1200–1450) time periods, which allowed us to examine changes in gene pools over time and to test these migration hypotheses. Comparing the full mitogenomes from 114 individuals, we show that low levels of migration occurred diachronically, although they still may have contributed to hybridized cultural practices. These data counter the long-standing assumption that widescale population replacement was the cause for the rise of Paquimé, the center of the Casas Grandes world in the thirteenth-century A.D.