Experts have disputed a study arguing that pre- Columbian people had little impact on the western central Amazon. Previously, a different study suggested that the early Amazon was inhabited by large, sophisticated populations influencing both the forest and its biodiversity. Soil samples were used in the new study to show the Amazon rainforest is more a product of nature than human influence.

The new study which was based on 247 soil samples taken from 55 locations, found little evidence of charcoal which is said to be an indicator of anthropogenic deforestation. The team also looked for phytoliths, microscopic silica that is deposited after a plant dies but they found no evidence of human-planted palm groves. Critics have said the study's sample size was far too small to get a holistic view of a region around the size of India (approximately 3 million square kilometers). The sample sites are also said to be  highly clustered and that sampling problems may have missed evidences for charcoal. While the discovery of phytoliths would provide evidence for anthropogenic landscape changes, some claim the study missed some of the region's most important crops. Further, those disputing the study say it goes against archeological excavations and some post Columbian writing.

Archeological digs of historical cattle ranches and soy farms in the Amazon have found large earthen structures, known as geoglyphs, which are believed to have been created by large, well-organized Amazonian civilizations.

Others have claimed that, in a 16th Century book about the Amazon, the German mercenary, Ulrich Schmeidel, described a complex world which was sometimes empty but densely populated at other times.

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