Amazonians Drastically Altered the Rainforest 3,500 Years Ago
In an article appearing in the 7 June 2021 edition of the Proceedings of the National Academy of Sciences ( PNAS), a team of researchers has revealed the results of an enlightening new study about land use practices of people who lived in the Amazon rainforest more than 3,500 years ago. Their conclusions contradicted the previous theory that ancient Amazonians had left the land largely untouched.
Uncovering Fascinating Data About Ancient Amazonians
According to UCF Today , the researchers from the University of Central Florida in the United States and Northumbria University in the United Kingdom uncovered fascinating data about the way Amazonians during the pre-Columbian era altered their landscape. Their research demonstrated that ancient Amazonians used and managed fire, as well as taking steps to increase the productivity of their farming and fishing activities.
To find out more about ancient land use, the scientists analyzed core samples of soil taken from the Llanos de Mojos region of northeastern Bolivia. They dug down 5 feet (1.5 m) deep into the earth to extract these samples, which took them back several thousand years in time.
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During their analysis, they detected changes in soil content and characteristics that couldn’t be traced to natural processes alone. This meant that ancient peoples in the Amazon had intentionally and significantly altered their landscape, in ways that are more commonly associated with modern integrated land management practices.
The researchers working in Llanos de Mojos, Bolivia, extracted two, five-foot long, cores of earth from two different locations in order to understand the ancient land use of the Amazonians. ( UCF)
Amazonians Altered Their Landscape to Adapt to Climate Change
The research team concluded that the Amazonians had undertaken these activities at a time when the climate was changing and becoming warmer and wetter. These strategies in some cases were designed to take advantage of climate change , and in other instances to offset their troublesome effects.
"This is the first time that we've been able to show in the past how people managed their land and water resources in a coupled system," explained Bronwen Whitney, an associate professor of geography and environmental sciences at Northumbria University who led the UK-based research team. "The intensification of plant, fire and water management occurred at the same time, which emphasizes how farming or fishing were equally important to the people of the region."
Past studies had found evidence of land alteration in the Amazon. But until now those activities were believed to have occurred much closer to modern times, starting no earlier than the year 300 AD (just 1,700 years ago).
3,500-Year-Old Evidence of the Land Use Practices of the Amazonians
This new research project was more in-depth and intensive than past studies and proved that the earlier timeline was nowhere near accurate. The new evidence suggests that people in the southwestern Amazon first began modifying their natural living environment at least 3,500 years ago, and most likely even before that.
In one core sample, traces of charcoal were found in a layer of earth that is more than 6,000 years old, dating to approximately 4,100 BC. More concentrated charcoal deposits were found in a layer dating to around 1,500 BC, and the researchers believe the latter can be more definitively linked to human activity. Since further analysis showed the climate was getting wetter at the same time charcoal deposits were getting thicker, naturally occurring fires are an unlikely explanation in this instance.
If the ancient Amazonians were making and managing fire, they would have been using it for a variety of reasons. They would have used it to cook food, make pottery, or provide a source of heat on cold nights. They would have also started fires to clear land for planting, or perhaps to flush out animals the people were hunting.
The most definitive signs of agricultural practice are the remains of 44,000 raised fields that have been found scattered throughout the Llanos de Mojos region. In ancient times, raised fields were necessary to avoid flooding, which became increasingly common as rainfall levels rose and wetlands expanded.
The paleoethnobotanist and lead author Neil Duncan (left) and the study co-author John Walker (right), both from UCF, concluded that 3,500 years ago Amazonians were in fact modifying their surrounding landscape. ( UCF)
Incredible Revelations About Amazonians Revealed from Core Samples
The core samples revealed traces of microscopic silica particles produced by corn and squash plants, some of which were dated to as early as 1,380 BC. These are the crops that would have been grown in the raised fields, starting at least 2,000 years before Europeans reached the Americas.
The people’s water management practices were also partially a response to climate change. Wet conditions encouraged crop growth, thereby creating a favorable environment for agriculture. But water also had to be drained from fields that were oversaturated following heavy rainfall or floods. Water needed to be diverted from areas where people were living, to make sure their homes were kept safe and dry.
One of the most fascinating discoveries in the area were the remains of many fish weirs. These underwater traps were commonly distributed around the edges of the Llanos de Mojos wetlands, where fish swimming by could be herded into fenced-in areas for easier harvesting. This advanced aquacultural system highlights just how innovative and inventive the people of the ancient Amazon were. They were determined they were to take full advantage of the bounty that nature provided.
While there continues to be a long-held belief that ancient Amazonians left the land untouched, this study concludes that they actually modified their natural environment quite extensively. ( gustavofrazao / Adobe Stock)
The Endlessly Inventive Culture of the Amazonians
Despite the fresh revelations, researchers of pre-history still have much to learn about the mysterious people who occupied the southwestern Amazon in ancient times. "This region has one the highest diversity of languages in the world, which reflects distinct ways of life and cultural heritage," said study co-author John Walker , an associate professor in the University of Central Florida’s anthropology department. "We know something about the last 3,000 to 4,000 years of, say Europe or the Mediterranean, but we don't have some of that same information for the people here. That makes this an incredible story waiting to be written."
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Moving forward, the researchers plan to fully investigate the function and history of the region’s fish weirs. They also want to apply the latest dating techniques to the raised fields and other earthworks, to help reveal more details about the ancient agricultural history of the area. While the European influence in Central and South America was profound, long before outsiders reached the Amazon, the Amazonians had developed their own unique cultures based on adaptations to the (constantly evolving) environments they lived in.
Thanks to this archaeological study of the Amazon , the researchers have concluded that Amazonians created their own systems for managing nature that included both active and passive elements. While their systems were more sustainable and less exploitative than the European model, they still encouraged significant human manipulation of the landscape to promote greater food security and improve survival odds.
Top image: Illustration representing the way the rainforest landscape was shaped by ancient Amazonians around 3,500 years ago. Source: Kathryn Killackey / UCF
By Nathan Falde