A major scientific question in the understanding of human population genetic diversity is how modern diversity has been shaped by sociocultural transitions and other major events in human history. These factors and their consequences are not well-understood, despite the potential for significant reshaping of the genetic makeup of human populations. This dissertation research by doctoral student Jaime Mata-Miguez (under the supervision of Dr. Deborah Bolnick, University of Texas at Austin) examines the demographic and genetic impact of cultural expansion and colonialism on human population genetics, investigating how factors such as community reorganization, altered migration patterns, and/or increasing mortality rates resulting from warfare and other forms of changed or destroyed traditional lifeways can produce profound genetic effects in impacted human populations.
To comprehensively address this research question, the project must focus on a human study population for which there are data on both these historical impacts and the genetic makeup of the ancient and present-day members of that population. By comparing DNA from ancient human remains and the present-day inhabitants of Xaltocan, Mexico, the genetic changes resulting from the multiple societal impacts associated with expansion of the Aztec empire and Spanish colonialism in Mesoamerica can be assessed. This is a unique test case for examining the impacts previously discussed; archaeological research at Xaltocan has unearthed both pre-Aztec and Aztec human remains with well-preserved DNA, so Xaltocan offers a unique opportunity to study genetic changes across the period of Aztec expansionism, while genetic comparisons between these pre-Hispanic samples and the modern residents also make it possible to clarify the genetic changes that occurred at Xaltocan after the onset of Spanish colonialism. As the first project to analyze genome-wide markers in both ancient and modern samples from a single location, the research will dramatically increase statistical power to infer past population history and to clarify how major societal disruptions impact our genetics, in addition to forces such as genetic drift and gene flow.
This project also contributes to an array of broader scientific and social impacts. By comparing ancient and modern DNA from Xaltocan, this investigation elucidates the genetic consequences of sociocultural change and shows how major historical events have shaped human genetic diversity in recent times. Genetic data and results are being disseminated through public databases, peer-reviewed publications, scientific presentations, articles in the popular press, and educational presentations to the Xaltocan community, enhancing scientific understanding and appreciation while contributing to the added value of these data for additional relevant research. Community collaboration and participation is a critical part of this project, fostering public engagement with science and promoting scientific literacy in indigenous communities. Finally, this study provides research, training, and mentorship opportunities for graduate and undergraduate students at the University of Texas at Austin, including increased participation of members of under-represented groups in science.