These causeway and mound settlement structures have been known for quite awhile, the new thing here seems to be the discovery of a more complex city like settle

These causeway and mound settlement structures have been known for quite awhile, the new thing here seems to be the discovery of a more complex city like settlement. It's seems like cities and complex states probably weren't necessary to build the causeways as evidenced by Poverty Point and the mound building peoples of Ohio and the later Mississippian/Cahokia. However, given the geography in that part of the Amazon basin, these mounds and causeways were probably necessary FOR cities to develop. The other piece is this quote: > By the 20th century, archaeologists had yet to confirm the rumours, and argued that the Amazon’s nutrient-poor soil was inadequate for supporting large-scale agriculture, and that it would have prevented tropical civilizations I think it's worth noting that a number of large settlements north of the Rio Grande managed to grow quite large with limited or no agriculture. Particularly where fish were plentiful, farming wasn't taken up even when contemporaneous neighboring groups farmed. Similar to Kosher or Halal, not farming seemed to be a matter of cultural or religious preference/edict among some pre-Columbian indigenous peoples.