Early human settlements were typically based on low-lying hills or mounds.
Five types of archaeological mound have been noted in the Amazon region: shell refuse and artificial mounds, artificial earth platforms for entire villages, earth mounds and ridges for cultivation, causeways and canals, and figurative mounds, both geometric and biomorphic.[29]
Shell mounds were the earliest; they represent piles of human refuse and are mainly dated between 7500 and 4000 BP. They all represent pottery age cultures; no preceramic shell mounds have been documented so far by archaeologists.
Figurative mounds are the latest chronologically.
Artificial earth platforms for entire villages are the second type of mounds. They are best represented by the Marajoara culture.
There is ample evidence for complex large-scale, pre-Columbian social formations, including chiefdoms, in many areas of Amazonia (particularly the inter-fluvial regions) and even large towns and cities.[30] For instance the pre-Columbian culture on the island of Marajó may have developed social stratification and supported a population of 100,000 people.[31] The Native Americans of the Amazon rain forest may have used Terra preta to make the land suitable for the large-scale agriculture needed to support large populations and complex social formations such as chiefdoms.[31]
Many indigenous tribes engaged in constant warfare. James Stuart Olson wrote: "The Munduruku expansion dislocated and displaced the Kawahíb, breaking the tribe down into much smaller groups... [Munduruku] first came to the attention of Europeans in 1770 when they began a series of widespread attacks on Brazilian settlements along the Amazon River.