A team of researchers from the U.S. and Brazil has created a virtual map of possible ancient human population centers in the Amazonian jungle by using statistical methods that connect modern terra preta areas. In their paper published in Proceedings of the Royal Society B: Biological Sciences, the team describes how they applied archeological site information with statistics to come up with a way to guess where other early population sites might be.
Despite years of work, modern scientists still don't really know much about the people that populated that Amazonian basin prior to the arrival of European explorers. The dense jungle growth has made it difficult to study the area, and the preponderance of poor soils suggests that the area could not have supported large groups of people anyway—the soil would not support the farming necessary to support them. In more recent times, some evidence (ancient roads and earthworks) has been uncovered that indicates that large settlements of people may indeed have indeed populated the area, which would have been made possible by a soil enrichment technique known as terra preta (adding nutrients that resulted in fertile "black earth" that can still be seen today.). Because very few terra preta sites have been found, researchers aren't sure if they are few and far between, or if there are more simply hidden in the jungle.
To find out, the researchers with this new effort created maps that displayed all of the known terra preta locations. They then noted geographical details about each site and discovered there were some possible correlations between them, e.g most tended to exist on bluffs overlooking rivers. Using such information, they applied statistical analysis to maps of the area and came up with a model that predicted where other terra preta locations may be found. Their results indicate that more than three percent of the total Amazonia basin may be hiding terra preta sites.
The team has not been able to test their maps yet, so it's not yet known how accurate their guesses may be, but the hope is that by uncovering more terra preta sites, more information can be gleaned from the area to help uncover chapters of human history in South America that until now have remained hidden.