Archaeologists have long debated the role of regional interaction during the 11th – 14th centuries at the Mississippian polity of Cahokia. Architectural styles, exotic materials, and cultural objects provide indirect evidence for cultural interaction and ethnic and social diversity; but absolute proof of this diversity was missing.

Researchers traditionally thought of Cahokia as a relatively homogeneous and stable population drawn from the immediate area, however identifying the movement of individuals (rather than materials) became key to a new study by Thomas Emerson, who led the new analysis. Emerson is Illinois state archaeologist and the director of the Illinois State Archaeological Survey at the University of Illinois and is helping to grow our understanding of the population that enabled formation of this unique polity.

Strontium isotope analysis

This study is the first to use strontium isotope analysis (87Sr/86Sr) of human tooth enamel to identify immigrants at Cahokia. Modern and archaeological fauna were used to establish a baseline “local” range of strontium isotope ratios for the American Bottom region surrounding Cahokia.

Teeth from individuals interred in diverse mortuary locations, including mounds, within this region were analysed and compared to the local strontium isotope range to identify individuals of non-local origin. One-third of all individuals analysed were identified as non-local, and the range and variability of their strontium ratios suggests multiple places of origin.

Role of migration

The correlation of isotopic data with available biological and mortuary evidence allows us to examine the role of migration in the history of this Mississippian polity.

“Increasingly archaeologists are realising that Cahokia at AD 1100 was very likely an urban centre with as many as 20,000 inhabitants,” he said. “Such early centres around the world grow by immigration, not by birthrate.”

READ THE ENTIRE ARTICLE HERE: Cahokia was a melting pot metropolis : Archaeology News from Past Horizons.