March 3, 2022

How climate change affected the population of this Maya settlement

A study led by McGill University has found that the Maya settlement in Itzan, now modern-day Guatemala, varied in size over time in response to climate change.

The findings, published in Quarternary Science Reviews in a study entitled “Molecular evidence for human population change associated with climate events in the Maya lowlands,” shows that both droughts and very wet periods led to impactful population declines, and suggests that the Maya settlement in Itzan started earlier and lasted longer than previously known.

Researchers were able to determine the ebb and flow of the Maya population by studying stanols, or organic molecules found in human and animal fecal matter, taken from samples at the bottom of a nearby lake.

By measuring the stanols, researchers were able to estimate changes in population size and examine how it aligns with information about climate variability and changes in vegetation taken from biological and archeological sources.

The study charted major Maya population changes in the area over a period starting 3,300 years ago, and identified shifts in settlement patterns that occurred over hundreds of years that are associated with changes in how the land was used and agricultural practices.

The evidence from the fecal stanol analysis suggests that humans were present on the Itzan escarpment about 650 years before the archeological evidence confirms it, the study states.

The data also showed that the Maya continued to occupy the area, in smaller numbers, after the a period of time referred to as the “collapse” between 800 to 1000 AD where it is thought that extended warfare or intense drought caused the entire population to desert the area.

Further evidence was found of a large population spike around the same time that records show a large population fleeing from the Spanish attack on the last Maya stronghold Nojpeten (modern-day Flores, Guatemala) in 1697, something not known before.

Traditionally, population estimates rely on archeological inspection and excavation of settlements which then feed into reconstructions of population dynamics, paired with pollen analysis and indications of soil erosion into lakes to reconstruct the ecological changes that took place at the same time, according to a release.

“This research should help archeologists by providing a new tool to look at changes that might not be seen in the archaeological evidence, because the evidence may never have existed or may have since been lost or destroyed,” said study author Benjamin Keenan in the release. “The Maya lowlands are not very good for preserving buildings and other records of human life because of the tropical forest environment.”

The fecal stanols from the lake sediment confirmed that the Maya population in the Itzan area declined due to drought at three distinctive periods: between 90 to 280 AD, 730 to 900 AD and during 1350 to 950 BC.

The study also suggests that the Maya people may have adapted to environmental issues like soil degradation and nutrient loss due to the climate changes by using human waste as fertilizer.

Researchers also found that the population declined during a very wet period between 400 and 210 BC, something previously not very well studied, the study notes, adding that the population decline in response to both dry and wet periods show there were climate-fuelled effects on the population at both climate extremes – not just drought.

“It is important for society generally to know that there were civilizations before us that were affected by and adapted to climate change,” said senior study author and assistant professor Peter Douglas in the release. “By linking evidence for climate and population change we can begin to see a clear link between precipitation and the ability of these ancient cities to sustain their population.”

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