Fossil pollen records from the Amazon hint at a surge of regrowth in forests of the Amazon basin around 300 to 600 years before European colonisation of South America, suggesting that Indigenous peoples may have been leaving the region at that time.
Following European arrival in South America in the mid-16th century AD, millions of Indigenous people lost their lives in the face of unfamiliar disease, slavery and warfare in an event known as The Great Dying of the Indigenous Peoples of the Americas.
Previous studies have shown a dip in carbon dioxide levels in the region in 1610, known as the Orbis spike. This has been associated with the population decline that occurred after Europeans landed in South America, as forests regrew on land previously inhabited by Indigenous people, decreasing carbon dioxide levels.
But the pollen record suggests forest regrowth in this region happened earlier. Mark Bush at the Florida Institute of Technology and his colleagues analysed sediment samples from 39 lakes in the Amazon, in Brazil, Peru, Ecuador and Bolivia. They recovered pollen from the lake sediment – the deeper the sediment, the older it is.
They found that forest regrowth in the Amazon basin may have begun around 300 to 600 years before the Orbis spike. They didn’t see a pattern of reforestation in the fossil records between 1550 and 1750, following European colonisation.
“Between 950 and 1350 AD, there are more sites that are gaining forest than losing forest during that time,” says Bush. This suggests that Indigenous people were abandoning land hundreds of years before Europeans arrived, he says.
“These were complex societies, they weren’t just hunter-gatherers,” says Bush. The researchers are unsure about the drivers of this early movement, but suggest climate change could have been at play.
Eduardo Góes Neves at the University of São Paulo in Brazil remains unconvinced, as the significant drop in carbon dioxide after European arrival cannot otherwise be explained. “There is extensive evidence for forest recovery from 1550 to 1750,” says Neves.
Journal reference: Science, DOI: 10.1126/science.abf3870
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