2023-05-17 13:15:56
Before European colonization, the territory we know today as Mexico was home to several civilizations in two main cultural zones: Aridoamerica in the north, inhabited mainly by hunter-gatherers; and Mesoamerica in the central and southern regions, where large cultures based on agriculture thrived.
The distinction between these two regions has normally been based on cultural characteristics, subsistence strategies and ecological aspects.
Archaeological evidence suggests that the boundary between these two regions moved south between 900 and 1300 AD, due to droughts that lasted several decades, presumably leading to the replacement of central Mexican populations by Arido-American peoples and perhaps to the abandonment of some Mesoamerican cities.
However, the nature of these social changes has been full of gaps and has only had archaeological evidence.
Although the study of the genetic variation of these ancient populations could help to clarify the uncertainties, the genomic data of the ancient pre-Hispanic populations of Mexico are very insufficient.
Mexico, with the evaporative stress index reflecting a recent drought. Similar situations occurred in the past. For example, between the years 900 and 1300 after Christ, droughts caused great population changes in Mexico. (Image: NASA Earth Observatory/Joshua Stevens/US Geological Survey/SERVIR)
Viridiana Villa-Islas, from the National Autonomous University of Mexico (UNAM), and her colleagues are making it possible to fill in many of these gaps. They have presented broad-spectrum whole-genome data from 12 individuals and 27 mitochondrial genomes from 8 archaeological sites in Mexico, 2 of them located on the shifting border between Aridoamerica and Mesoamerica.
Contrary to what the archaeological data show, Villa-Islas and his colleagues reveal population continuity during the mega-drought period and a great conservation of the genetic structure of the population during the last 2,300 years, up to present-day Mexico. This genetic structure can still be observed in modern indigenous populations.
In addition, the study authors have also identified a contribution to the pre-Hispanic populations of northern and central Mexico from two unsampled ancient “ghost” populations, demonstrating that the demographic events that gave rise to the Aridoamerican and Mesoamerican populations are more complex than what was previously thought.
The study is titled “Demographic history and genetic structure in pre-Hispanic Central Mexico”. And it has been published in the academic journal Science. (Source: AAAS)
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