Jul 18, 2019 | Updated: 09:53 AM EDT

Abrupt Climate Change Led to a Dramatic Decline in South American Populations 8,000 Years Ago

May 09, 2019 01:47 PM EDT

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Abrupt Climate Change Led to a Dramatic Decline in South American Populations 8,000 Years Ago
(Photo : Image by Pete Linforth from Pixabay)

A new UCL research suggested that abrupt climate change some 8,000 years ago led to a dramatic decline in early South American populations. Published in Scientific Reports, the study 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.

Dr. Philip Riris at UCL Institute of Archaeology, the lead author of the study said that 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. The study aimed 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.

Dr. Riris added that unpredictable levels of rainfall, especially in the tropics, appear to hurt pre-Columbia populations until 6,000 years ago, after which recovery is evident. The recovery seems to correlate with cultural practices surrounding tropical plant management and early crop cultivation, possibly acting as buffers when wild resources were less predictable.

The focus of the research was on the transition to the Middle Holocene itself that spanned 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.

Though it was revealed in the study that there was a significant disruption to population, the research highlighted that indigenous people of South America were thriving before and after the middle Holocene.

In this new research, the team of archaeologists investigated data from nearly 1,400 sites consisting of more than 5,000 radiocarbon dates to understand how the population changed over time and cross-referenced this information with climate data.

Dr. Riris explained that they studied ancient records of rainfall including marine sediments for evidence of exceptional climate events. Within windows of 100 years, they compared the Middle Holocene to the prevalent patterns before and after 8,200 years ago. Typical modes of rainfall suggest on average an unusually dry or wet year every 16 - 20 years, while under highly variable conditions this increases to every five years or so. This analysis puts into perspective the challenge that indigenous communities would have faced.

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

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