Amazon lost a large part of its population before the arrival of Europeans, pollen analysis shows – 04/29/2021 – science

The Amazon may have lost a significant part of its population a few centuries before the arrival of Europeans on the American continent. This emerges from an analysis that has attempted to estimate the fluctuations of the Amazon vegetation over time.

It is not yet clear why the region has changed in the past, which is considered to be one of the main population centers in pre-Columbian America. Previous epidemics or wars between indigenous groups may also have contributed to relative depopulation. In addition, the data gathered through the survey did not show such marked changes in the 16th and 17th centuries, although this was expected as the native population was decimated by the diseases and weapons that Europeans brought with them during this period.

The study has just been published in the journal Science, one of the most important in the world. One of its authors is the Brazilian Majoi Nascimento, who conducts post-doctoral research at the Institute for Biodiversity and Ecosystem Dynamics at the University of Amsterdam. The international team responsible for research, coordinated by Mark Bush from the Florida Institute of Technology, also includes scientists from Costa Rica, Mexico and other European countries.

To estimate the population fluctuations in the Amazon over the past 2,000 years, the researchers used pollen layers from 39 lakes spread across the region in an arc that extends from Ecuador and Bolivia to near the island of Marajó.

As each type of plant produces pollen grains with unique properties, the layers serve as a record of changes in vegetation over the centuries. Archaeological data show that since the beginning of the Christian era, the practice of farming and building villages in the area has increased, in part due to the production of monumental structures such as man-made hills and large roads. It is estimated that the Amazon population reached 8 million people at the height of the process. In order for these transformations to take place, the ancient Indians had to convert part of the forest into crops that, over time, would appear in the pollen composition of the lakes.

On the other hand, some researchers believe that the area covered by forest increased sharply in the first centuries after contact with Europeans due to the high death toll of indigenous groups, which would have led to the abandonment of villages and crops. This phenomenon is sometimes suggested to explain a significant decrease in the concentration of carbon dioxide in the atmosphere at the beginning of the 17th century. In this case, the forest would have absorbed the gas as it grew again and further accentuated a phase of cooling the global temperature (since carbon dioxide, as it is also known, warms the atmosphere). If this idea were correct, the colonial-era genocide would have even changed the earth’s climate.

However, the new research shows a more complex situation. Majoi Nascimento explains that in addition to analyzing pollen, the team also took into account the presence of coal, a material that is usually a clear sign of human occupation in the Amazon (as the forest in the region does not generally ignite spontaneously). In the case of pollen grains, the presence of the genus Cecropia (popularly Embaúbas) was an important indicator. They are fast growing trees that need sunny environments. In other words, the presence of high levels of Embaúba pollen may indicate that an area previously cleared for planting or building villages has been abandoned by humans and is being taken over by the forest.

Although 80% of the 39 lakes showed signs of human occupation prior to the arrival of Europeans, the record of pollen and coal shows different trends over time. At the time, between AD 1550 and 1750, the greatest impact of Native American-invader contact should have occurred was the number of places where forest pollen increased (i.e. fewer people were occupied) more or less equal to lakes where forest pollen decreased (hence more plantations). The effect that would be expected from the abandonment of the sites by humans occurs more strongly in a larger area between the years 950 and 1350.

“There was always the idea that the Amazon peak was at its highest just before the arrival of Europeans, but some archaeological data already showed that this couldn’t be true. Our work reinforces this, ”says Nascimento. “It is clear, however, that this does not mean denying the negative effects of contact on the population of our continent. We see the weight of these effects in other regions and even in the Amazon, it is undeniable. “

“The article brings more evidence challenging the narrative that the Amazon population would be on an uninterrupted growth path until contacted by Europeans. This should come as no surprise, as cycles of growth and collapse are confirmed in other parts of America well before 1492. The Maya case is perhaps the most obvious example, ”says archaeologist Jonas Gregorio de Souza, a Brazilian who works at the Pompeu Fabra University in Barcelona.

“I do not fully agree with the conclusions of the article, but I think it is good that it is being published because it is a huge synthesis of data,” analyzes Eduardo Góes Neves of the USP’s Museum of Archeology and Ethnology. “The results that point to the lack of deforestation in the 16th and 17th centuries are not clear to me.” On the other hand, Neves points out that the data on the decline around the year 1000 of the Christian era agrees reasonably well with archaeological studies.

“This was a time of profound change, particularly in the central Amazon in Santarém [no Pará] and in the Amazon estuary. New ceramic styles emerge, monumentality appears in some places and disappears in others, ”he explains. Some of these changes suggest potential conflicts, such as the emergence of ditches and palisade fortified villages and the reduction in the area of ​​these villages, which would help explain the population decline.

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