Human settlements in Amazonia much olderthan previously thought24 April 2019

Excavations at the site of La Chacra. Credit: JoséCapriles, PSU

Humans settled in southwestern Amazonia andeven experimented with agriculture much earlierthan previously thought, according to aninternational team of researchers.

"We have long been aware that complex societiesemerged in Llanos de Moxos in southwesternAmazonia, Bolivia, around 2,500 years ago, butour new evidence suggests that humans firstsettled in the region up to 10,000 years ago duringthe early Holocene period," said Jose Capriles,assistant professor of anthropology. "These groupsof people were hunter gatherers; however, ourdata show that they were beginning to deplete theirlocal resources and establish territorial behaviors,perhaps driving them to begin domesticating plantssuch as sweet potatoes, cassava, peanuts andchili peppers as a way to acquire food."

The archaeological team conducted its study onthree forest islands—Isla del Tesoro, La Chacra andSan Pablo—within the seasonally flooded savannaof the Llanos de Moxos in northern Bolivia.

"These islands are elevated above the surroundingsavanna, so they do not flood during the rainyseason," said Capriles. "We believe people wereusing these sites recurrently as seasonal camps,particularly during the long rainy seasons whenmost of the Llanos de Moxos become flooded."

Excavation team taking measurements duringexcavations. Credit: José Capriles, PSU

The team's excavations of the forest islandsrevealed human skeletons that had been

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intentionally buried in a manner unlike that of typicalhunter gatherers and instead were more akin to thebehaviors of complex societies—characterized bypolitical hierarchy and the production of food. Theirresults appear today in Science Advances.

"If these were highly mobile hunter gatherers youwould not expect for them to bury their dead inspecific places; instead, they would leave theirdead wherever they died," said Capriles.

Capriles noted that it is rare to find human or even archaeological remains that predate the use of firedpottery in the region.

"The soils tend to be very acidic, which often makesthe preservation of organic remains very poor," hesaid. "Also, organic matter deteriorates quickly intropical environments and this region completelylacks any type of rock for making stone tools, soeven those are not available to study."

Samples collected from the excavation site. Credit: JoséCapriles, PSU

Collection of sedimentary cores in the forest island SanPablo, in the picture, Dr. Umberto Lombardo. Credit:José Capriles, PSU

Human burials exposed and recovered during thearchaeological excavations at the forest island of La

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Chacra during excavations. Credit: José Capriles, PSU

Burial in La Chacra exposed during archaeologicalexcavations. Credit: José Capriles, PSU

According to Umberto Lombardo, earth scientist atthe University of Bern, when the researchers firstpublished their discovery of these archaeologicalsites in 2013, they had to base their conclusions onindirect evidence—mostly geochemicalanalyses—rather than direct evidence such asartifacts.

"Because of the lack of direct evidence manyarchaeologists were skeptical about our findings,"said Lombardo. "They did not really believe thatthose forest islands were early Holocenearchaeological sites. The current study providesstrong and definitive evidence of theanthropocentric origin of these sites, because thearchaeological excavations uncovered earlyHolocene human burials. These are the definitiveproof of the antiquity and origin of these sites."

Capriles noted that the human bones on theseforest islands were preserved despite the poorconditions because they were encased withinmiddens—or trash heaps—containing abundantfragments of shell, animal bones and other organicremains.

"These people were foraging apple snails duringthe wet season and disposing of the shells in largeheaps, called middens," said Capriles. "Over time,water dissolved the calcium carbonate from theshells and those carbonates precipitated over thebones, effectively fossilizing them."

Mapping during the archaeological excavations at the siteof La Chacra. Credit: José Capriles, PSU

Because the human bones were fossilized, theteam was unable to date them directly usingradiocarbon dating. Instead, they used radiocarbondating of associated charcoal and shell as a proxyfor estimating the time range that the sites wereoccupied.

"The abundant remains of burned earth and woodsuggests that the people were using fire, likely toclear land, cook food and keep warm during longrainy days," said Capriles.

According to Capriles, a gap exists between thepeople his team studied who lived on the forestislands between 10,000 and 4,000 years ago andthe rise of complex societies, which began around2,500 years ago.

"This paper represents the first step in the effort tolearn more about the people who inhabitedsouthwestern Amazonia for thousands of years butwe know nothing about," said Lombardo.

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Capriles added, "Are the people we found directpredecessors of those later, more complexsocieties? There are still questions to be answeredand we hope to do so in future research."

More information: J.M. Capriles at PennsylvaniaState University in State College, PA el al.,"Persistent Early to Middle Holocene tropicalforaging in southwestern Amazonia," ScienceAdvances (2019). advances.sciencemag.org/content/5/4/eaav5449

Provided by Pennsylvania State UniversityAPA citation: Human settlements in Amazonia much older than previously thought (2019, April 24)retrieved 29 August 2021 from https://phys.org/news/2019-04-human-settlements-amazonia-older-previously.html

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