lunes, 17 de marzo de 2014

Cahokia was a melting pot metropolis (EEUU)

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.”
The new analysis, reported in the Journal of Archaeological Research, tested the chemical composition of 133 teeth from 87 people buried at Cahokia during its heyday. The researchers looked specifically at strontium isotope ratios in the teeth and in the remains of small mammals from the same area.
“Strontium isotope ratios in rock, soil, groundwater and vegetation vary according to the underlying geology of a region,” the researchers wrote. “As an animal eats and drinks, the local strontium isotope composition of the water, plants and animals consumed is recorded in its skeletal tissues.”
Strontium signatures may not be unique to a location, Emerson said, but the ratios in a person’s teeth can be compared to those of plants and animals in the immediate environment.
“Teeth retain the isotopic signature of an individual’s diet at various periods of life depending on the tooth type sampled, ranging from in utero to approximately 16 years of age,” the researchers wrote.
The strontium signature in the teeth can be compared to that of their place of burial, to determine whether the person lived only in that vicinity. Early teeth and later teeth may have different strontium signatures, an indication that the person immigrated.

One-third of the population

By analysing the teeth of those buried in different locations in Cahokia, Emerson, state archaeological survey bioarchaeologist Kristin Hedman and graduate student Philip Slater discovered that immigrants formed one-third of the population of the city throughout its history (from about AD 1050 through the early 1300s).
“This indicates that Cahokia as a political, social and religious centre was extremely fluid and dynamic, with a constantly fluctuating composition,” Emerson said.
The findings contradict traditional anthropological models of Cahokian society that are built on analogies with 19th-century Native American groups, Emerson said.
“Cahokia, because it was multi-ethnic and perhaps even multilingual, must have been a virtual ‘melting pot’ that fostered new ways of living, new political and social patterns and perhaps even new religious beliefs,” he said.

Source: Past Horizons:

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