🏛️ This Maya city had everything, yet it also disappeared - why?

The collapse of the Maya civilization in the lowlands of Central America rests on a curious paradox. Between the years 750 and 900, many regions suffered repeated droughts, accompanied by a sharp demographic decline. Yet, at the site of Itzan in Guatemala, the population also decreased, but without any local trace of drought. This observation challenges explanations that rely solely on climate.

A team, led by Benjamin Gwinneth from the University of Montreal, conducted work at this site. By studying sediment cores from the nearby lake, they were able to reconstruct a 3,300-year timeline. Their approach is based on chemical markers that betray agricultural fires (slash-and-burn), types of vegetation, and human density, thus showing past interactions between populations and their environment.


The results show a marked evolution in Maya agricultural practices. During the Classic period, indicators of slash-and-burn decrease sharply while the population increases. This phenomenon indicates a shift to intensive methods, for example raised-field agriculture, to optimize already cleared lands and support growing urbanization. This adaptation reveals an organized society, capable of modifying its strategies to feed more inhabitants.

The examination of hydrogen isotopes in the sediments holds another surprise. Unlike other Maya areas further north, Itzan's climate remained stable, benefiting from regular rainfall due to orographic currents. This local climatic stability therefore rules out drought as a direct cause of the decline at this site, which poses a question for historians.

The researchers propose the idea that the interconnection of Maya cities may have played a determining role. Trade networks, political alliances, and migrations meant that a crisis in one region, such as a distant drought, could trigger conflicts, economic disruptions, and population movements affecting even spared areas. Thus, Itzan may have declined due to instability that spread across the entire Maya territory.

These discoveries, presented in the journal Biogeosciences, open new avenues for understanding the collapse of civilizations. They encourage taking into account social and economic dynamics, alongside environmental factors, to grasp how interconnected societies react to transformations.

Analysis of lake sediments

This scientific method involves extracting mud cores from the bottom of lakes to study the layers accumulated over time. Each stratum contains chemical markers, such as polycyclic aromatic hydrocarbons, which reveal the intensity of land-clearance fires. Leaf wax compounds provide information on vegetation types and rainfall patterns, while fecal stanols give clues about human population density.

By combining these indicators, researchers can reconstruct environmental changes and human activities over millennia. For example, at Itzan, the data show the appearance of the first permanent settlements 3,200 years ago, with an increase in slash-and-burn and population. This approach provides a precise timeline, allowing the linking of climatic events with social evolutions, without the need for often fragmentary written records.

Sediment analysis proves particularly useful for ancient civilizations like the Maya, where material traces are limited. It allows the quantification of agricultural practices, such as the shift from slash-and-burn to more intensive techniques, and the detection of local climatic phenomena. In this way, this method constitutes an objective basis for testing historical hypotheses and understanding how societies adjusted to their environment.