While the Amazon rainforest may look wild and unfamiliar, a new comprehensive study has revealed that it is actually the result of some of humanity’s first experiments with agriculture. Humans have lived in the Amazon for over 10,000 years and have built some of the greatest civilizations of the ancient world. They also dramatically changed the Amazon rainforest in ways that are still evident today.
Environmental researcher Carolina Levis of Wageningen University and a large international team of ecologists and archaeologists collaborated on a study for Science that will undoubtedly change our view of the Amazon. “Humans arrived in the Amazon at least 10,000 years ago and started using the species that were there. And more than 8,000 years ago, they selected some individuals with specific phenotypes that are useful to humans,” Levis told the Atlantic Oceanfrom Robinson Meyer. “They really cultivated and planted these species in their own gardens, in the forests they managed.” These early cultivators were taming trees at about the same time that Neolithic peoples in the Levant first tamed wheat and barley.
Working with data from the Amazon Tree Diversity Network, Levis and her colleagues identified 85 domesticated tree species of the Amazon’s 4,962 species. But these 85 species had an inordinate influence on the composition of the forest itself. “We found that 20 of these 85 domesticated species are hyperdominant: five times higher than the number of hyperdominant species expected by chance,” they write in Science. Overall, about 20 percent of all species in the Amazon rainforest today are the result of ancient domestication. In areas where great ancient civilizations existed, the number of servants is closer to 30 percent.
Favorite trees of Amazon people 8,000 years ago included rubber, cacao, brazil nut, caimito, acai palm, cashew, and tucuma palm. These trees and others were essential as food and building material for pre-Columbian societies.
In addition to evidence that these trees were cultivated and planted by humans, researchers found that housewives were particularly common around ancient cities identified by archaeologists, as well as along rivers where people lived in villages. Many could also be found in areas where Amazonian peoples engaged in slash-and-burn techniques to clear the land. It is possible that these species grew best in areas disturbed by human habitation. In other words, the density of domesticated trees likely resulted from a combination of intentional farming and species that readily adapted to human environments.
The result is a forest that has been heavily modified by man for thousands of years. Although ancient city builders left the forests more than a millennium ago and European colonization 500 years ago wiped out many surviving Amazonian peoples, these tree nurseries have left indelible marks on the landscape.
Although the forest has covered most of the areas where humans once built great temples, humans can still help some species become hyperdominant. Speak with Erin Ross on Nature, paleoecologist Crystal McMichael of the University of Amsterdam noted that the transformation of the Amazon did not end after contact with Europe. “It’s pretty common knowledge that ancient humans and modern humans both settle in similar areas,” she said. As new people pour into the woods, they are likely to keep the percentage of servants higher than average.
Scientists have long argued that humans played a role in shaping the Amazon. But what’s incredible about Levis and her colleagues’ research is that it’s a large-scale assessment of the Amazon that incorporates the perspectives of environmental scientists and archaeologists. This interdisciplinary work has enabled us to understand that a seemingly pristine wilderness is actually a patchwork of farms abandoned centuries ago.
Science2017. DOI: 10.1126/science.aal0157