The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)

Ancient DNA evidence of population replacement following the Aztec conquest of Xaltocan, Mexico


1Department of Anthropology, University of Texas at Austin, 2Department of Anthropology, Northwestern University

Friday 4:45-5:00, Parlors Add to calendar

The Otomi city-state of Xaltocan was an influential polity in central Mexico in the 11th-14th centuries, but its preeminence declined when it was conquered by the neighboring city of Cuauhtitlan in 1395. According to colonial documents, the Otomi population abandoned Xaltocan at this time and the site remained uninhabited until it was incorporated into the Aztec empire in 1428 and repopulated by the Aztecs. However, more recent archaeological finds (e.g., burials dated to the supposed abandonment period and continuity in the location of residential and funerary constructions) suggest that a significant portion of the Otomi population may have remained at Xaltocan after 1395 and even under Aztec rule.

To help resolve questions about population replacement at Xaltocan during this period, we extracted ancient DNA from 21 individuals recovered during archaeological excavations in Xaltocan. These individuals were buried outside houses in a mound containing stratified domestic deposits, and they can be divided into two temporal subpopulations (before and after AD 1395). We determined mitochondrial DNA haplogroups through RFLP analyses and constructed haplotypes based on 359 bp of HVR1 sequence. All results were verified through multiple independent extractions and amplifications.

Network analyses showed that distinct haplotypes were present in each subpopulation, and a test of population differentiation rejected the null hypothesis of population continuity. We also used computer simulations to further evaluate the evidence for population replacement. Altogether, our results suggest that the matrilines at Xaltocan underwent a significant replacement event after 1395.

This study was funded by NSF (#BCS-0612131 to E.R.) and the Pedro BarriƩ de la Maza Foundation (fellowship to J.M.-M.).

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