Pre-Columbian earth-builders settled along the entire southern rim of the Amazon

Southern-rim fortified villages dated ~AD 1250–1500, with a stated-assumptions population model

what the source states

"The results show that an 1800 km stretch of southern Amazonia was occupied by earth-building cultures living in fortified villages ~Cal AD 1250–1500." And: "Assuming site contemporaneity, the total population calculated for the UTB sites was 21,340… projected to the total area of potential occurrence of ditched enclosures in the SRA, the result is a population of 463,555… When projected to the total area of the SRA predicted to contain earthworks, the result is 1,087,150 inhabitants. Therefore, we assume that a population between ~500 thousand and 1 million for the SRA in late Pre-Columbian times (Cal AD 1250–1500) is a reasonable estimate."

limitations

• Population figures rest on site contemporaneity, ethnographically-derived formulae, and MaxEnt-projected extrapolation — all stated by the authors.