Abrupt Climate Change 8,000 Years Ago Led To Dramatic Population Decline In South America

8,200 years ago, inhabited sites in various places across South America were suddenly abandoned.

According to reports, abrupt changes in Earth’s climate around 8,000 years go let to a catastrophic decline in early South American populations.

As revealed in a  recent study by scientists from the UCL published in the journal scientific reports, there is evidence of a ‘widespread’ decline in the general population from 8,000 to 6,000 years ago.

“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,” revealed lead author, Dr. Philip Riris (UCL Institute of Archaeology) in a statement.

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“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. This recovery appears to correlate with cultural practices surrounding tropical plant management and early crop cultivation, possibly acting as buffers when wild resources were less predictable,” added Dr. Riris.

Scientists focused on the transitional phase to the Middle Holocene, spanning between 8,200 and 4,200 years ago.

This period was particularly important since it was then when hunter-gatherer populations on the American continent were experiencing changes in their lifestyle as the started domesticating plants, and creating new cultural habits that suited both the landscape and climate change.

The research led by UCL experts shows that there was a significant disruption in the population, although indigenous people in Soth America thrived before and after the middle Holocene.

“In the years leading up to population decline, we can see that population sizes were unharmed. This would suggest that early Holocene populations, probably with a social memory of abrupt climate change during the Pleistocene-Holocene transition, developed successful strategies to deal with climate change,” explained Dr. Manuel Arroyo-Kalin from the UCL Institute of Archaeology, and co-author od the study.

“Abandonment of certain regions and the need to adapt quickly to new circumstances may have promoted the exploration of alternative strategies and new forms of subsistence, including the early adoption of low scale cultivation of domestic plants. Viewed in the context of at least 14,000 years of human presence in South America, the events of the Middle Holocene are a key part of indigenous South Americans’ cultural resilience to abrupt and unexpected change,” Dr. Arroyo-Kalin added.

The researchers examined data gathered from more than 1400 sites with more than 5,000 radiocarbon dates, cross-referencing the information with climate data.

Dr. Riris explained: “We studied ancient records of rainfall such as marine sediments for evidence of exceptional climate events.  Within windows of 100 years, we compared the Middle Holocene to the prevalent patterns before and after 8,200 years ago. Normal patterns of rainfall suggest on average an unusually dry or wet year every 16-20 years, while under highly variable conditions this increases to every 5 years or so. This puts in perspective the challenge that indigenous communities would have faced.”

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