Tampa Bay pottery reveals Mississippian migrants

For decades, archaeologists have puzzled over Mississippian-style pottery found in Tampa Bay, far from the culture's core in the Mississippi River Valley. The decorated shards looked like they belonged to a society known for maize agriculture, shell-tempered pottery, and massive earthen mounds, but Tampa Bay's Safety Harbor communities did not grow maize or use shell tempering. Some experts thought the pottery was imported through trade; others suspected local imitation. A new study, reported by ScienceDaily, points to a third explanation: potters themselves moved south.

The researchers, led by Trevor Duke of the University of Florida and based at the Florida Museum of Natural History, analyzed 58 plain and decorated pottery fragments from Tampa Bay. First, they used neutron activation analysis to measure the pottery's chemical makeup and compared it with local clay deposits. The chemistry matched, showing the vessels were made from Tampa Bay clay, not shipped from the heartland. Then they used petrography, polishing thin slices of the fragments to half the width of a human hair, to examine them under a polarizing microscope.

That microscopic look revealed a telling difference. About 80% of the decorated pottery contained grog, crushed fragments of older pottery used as temper, a common Mississippian technique. None of the plain pottery contained grog; instead, the plain vessels used sand or dry clay, materials local potters had used for roughly 3,000 years. The decorated vessels were also built by coiling clay, while plain vessels were molded. In addition, within the grog, the team found mica, a mineral common in the Florida Panhandle but rare around Tampa Bay. The surrounding clay was local, but some crushed material came from the Tallahassee Hills, about 200 miles north.

"The chemistry matched, showing that the vessels had been produced locally," ScienceDaily reports, and the mica inside the grog points to the northern heartland.

The presence of multigenerational grog, where one piece of grog contains a still older piece, suggests more than just practical tempering. "It's sort of like Russian nesting dolls because you have grog within grog within grog," said Neill Wallis, curator at the Florida Museum and a co-author. "They're crushing up the same decorated vessels that include pieces of decorated pottery from before." The migrants apparently carried decorated pots from their homeland, then crushed them and mixed them into new clay, embedding physical links to their origin in every new vessel.

The researchers argue these potters brought specialized knowledge that gave them a niche in their new community. High-quality decorated pottery, made with better clay and more consistent recipes, was likely prized. The techniques remained confined to a small group for centuries, never spreading to plain pottery. Wallis suggests the knowledge was maintained as a kind of open secret: the potters had to broadcast enough to attract respect, but not enough to teach the craft.

Andrea Torvinen, collections manager at the Ceramic Technology Lab, said specialized skills are passed down through direct relationships with a mentor. "In this case, there could have been a more meaningful reason behind it. By tying the homeland pottery into this enchainment, they're bringing those pots with them into the next generation."

The study was published in American Antiquity. It resolves a debate that began more than 100 years ago, when archaeologists first noticed Mississippian-looking pottery in Florida's peninsula.

• archaeology
• Florida Museum of Natural History
• Mississippian culture
• pottery
• Tampa Bay
• Trevor Duke