Final answer:
Cyrus Thomas concluded that the ancient mounds in the American Midwest were built by the indigenous Mississippian culture for ceremonial, burial, and residential purposes, debunking the myth that they were created by a more 'advanced' civilization.
Step-by-step explanation:
Cyrus Thomas was a 19th-century archaeologist who studied the origins of the ancient mounds in the American Midwest. Through his research, he concluded that these mounds were indeed created by the indigenous peoples of North America, countering the prevailing myth at the time that such sophisticated earthworks could not have been the work of so-called 'primitive' Native American cultures. Thomas's work demonstrated that the Mississippian culture, pre-Columbian inhabitants of the Mississippi Valley, were the mound builders, responsible for the creation of various ceremonial, burial, and residential earthworks.
The Mississippian peoples were known for their mound-building activities, which included constructing enormous earthworks for a variety of purposes. Some of these mounds served as burial mounds for the elite, while others had residential uses with the chief and the elite living atop them. The largest mounds were often used as religious centers within the most significant towns of the chiefdoms, reflecting the complex social and religious structures of the Mississippians.