Oysters and oyster reefs are important components in the rich and productive southeastern US marsh-estnarine ecosystems. In recent decades, ecological research has shown that these complex systems can be driven by external biotic and abiotic perturbations or internal system dynamics that cause the system to rapidly reorganize into another alternate state or regime. Such shifts may have happened on a much larger scale several thousand years ago along the southeastern coast of North America. Beginning about 4,500 B.P., the coastal Native Americans built complex structures or oyster shell rings on the landward side of the southeastern sea islands of South Carolina, Georgia, and Florida. The construction of shell rings is believed to symbolize the conversion of nomadic hunter-gatherers to coastal fisherfolk and is considered a pivotal stage in the evolution of preEuropean contact culture in the United States. But, by about 3000 B.P., the shell rings were abandoned and the Native Americans dispersed. With the objective of learning from the past to help manage for the future, the Fig Island and Sewee shell ring systems near Charleston, South Carolina are analyzed using ecological comparisons with modern oyster systems, published archaeological and geological data, as well as reverse engineering approaches. In just a few years, the Indians built the Fig Island 1 shell ring using over 1.2 billion oysters. Had these oysters not been removed from the system, they would have cleared or filtered a water volume the size of North Inlet estuary near Georgetown, South Carolina about 6 times per day. This exercise examines the evidence on how the prehistoric system might have changed or shifted in response to the massive removal of oysters to build shell rings and concurrent changes in the natural environment.