Institute of Archaeology


Decline in ancient South American populations due to abrupt climate change

11 May 2019

Abrupt climate change some 8,000 years ago led to a dramatic decline in early South American populations according to UCL Institute of Archaeology researchers.

Patagonia, South America. Credit: Celine Harrand via Flickr

The new study, published in Scientific Reports, is the first to demonstrate how widespread the decline was and the scale at which population decline took place 8,000 to 6,000 years ago

The study focused on the transition to the Middle Holocene (itself spanning 8,200 and 4,200 years ago), a period of particularly profound change when hunter-gatherer populations were already experimenting with different domestic plants, and forming new cultural habits to suit both landscape and climate change. Data from nearly 1,400 sites were examined, consisting of more than 5,000 radiocarbon dates, to understand how population changed over time, and this information was cross-referenced with climate data.  The results showed that erratic rainfall had large scale impact across the region.

According to Philip Riris, the lead author of the study:

"Archaeologists working in South America have broadly known that some 8,200 years ago, inhabited sites in various places across the continent were suddenly abandoned. In our study we wanted to connect the dots between disparate records that span the Northern Andes, through the Amazon, to the southern tip of Patagonia and all areas in between. Unpredictable levels of rainfall, particularly in the tropics, appear to have had a negative impact on pre-Columbian populations until 6,000 years ago, after which recovery is evident."

While the research shows that there was a significant disruption to population, the study highlights that indigenous people of South America were thriving before and after the middle Holocene. It is believed that the research offers crucial historical context on how ancient indigenous South American populations dealt with climate change.

Manuel Arroyo-Kalin, co-author of the study, indicated:

Our study brings a demographic dimension to bear on understandings of the effects of past climate change, and the challenges that were faced by indigenous South Americans in different places. This understanding gauges the resilience of past small-scale productive systems and can potentially help shape future strategies for communities in the present."

The research was funded by a UCL CREDOC grant, the Sainsbury Research Unit at University of East Anglia and a British Academy Postdoctoral Fellowship at UCL.

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