Crushed pottery in 80% of decorated sherds in a 58-sherd Tampa Bay sample points to potters who moved in from the north

Roughly 80% of the decorated pottery fragments in a 58-sherd Tampa Bay sample contained grog, which is crushed old pottery mixed into fresh clay, and none of the plain fragments did. Archaeologists at the Florida Museum of Natural History read that split as the signature of migrant potters who arrived from farther north and kept making vessels their own way. The result gives a new kind of evidence to an argument that has run for generations.

Grog in the fancy pots, never in the plain ones

The work comes from a team led by C. Trevor Duke, who began it as doctoral research at the University of Florida, with Neill Wallis and Andrea Torvinen of the Florida Museum. The sample came from the Tampa Bay region. The 80% figure describes that sample, not every pot ever made around the bay.

According to the museum’s research announcement, the sample held 58 plain and decorated sherds from the Tampa Bay region, and about 80% of the decorated ones contained grog while no plain sherd did. Two laboratory methods carried the argument. Neutron activation analysis measured the chemistry of the clay and matched it to raw clay sources in the region, which shows the vessels were made locally rather than carried in. Petrography, using thin sections ground to about half the width of a human hair and viewed under a polarizing microscope, then identified what had been added to the clay. That second step is where the pattern appeared. Plain wares in the sample were tempered with sand or lumps of dry clay, a recipe the museum says had been used in the region for about 3,000 years. Duke said the grog tempering was something the team had not seen before, in earlier work or in the plain Tampa Bay samples.

Mica in the grog and the road to the Tallahassee Hills

The strongest clue to origin is a mineral. Mica turned up inside the grog, and mica is common in the Florida Panhandle but not typically found in peninsular Florida. That suggests the crushed pottery itself, not only the technique, came from farther north, from the direction of the Tallahassee Hills, about 200 miles away and the site of the nearest massive Mississippian mound center, as the ScienceDaily copy of the release notes.

Some of the grog fragments held smaller grog fragments of their own. The researchers interpret that as old pottery from the migrants’ homeland, broken up and reused across several generations. Wallis offered an image for it: “It’s sort of like Russian nesting dolls,” with grog nested inside grog inside grog.

The study, titled “Secret Recipes: Potting Knowledge and Migration in Mississippian (ca. AD 1000-1600) Tampa Bay, Florida, USA,” appeared in American Antiquity in 2026, with a journal page at Cambridge University Press. Funding came from the National Science Foundation, the Wenner-Gren Foundation, the Francis and Gertrude Levett Foundation and the Florida Archaeology Professorship at the Florida Museum.

Coiled and molded: two ways of making a pot in one bay

Grog was not the only difference. According to the museum, the decorated vessels were built by coiling, a Mississippian method, and followed more consistent paste recipes, while the plain wares were molded, a simpler technique that became more common as the local population grew. The decorated pots also used higher-quality clay than the plain ones, and the museum notes that decorated pottery was probably reserved for special occasions. Those layered contrasts matter because a single trait could be borrowed. A local potter might copy a shape or a stamped pattern after seeing it. A whole bundle of choices, including where the clay came from, what went into it and how the walls were raised, is harder to pass along without someone who learned it hands-on. Torvinen framed the human side in the museum’s account, saying migrant communities often had to figure out their own niche in a new place. The researchers read the decorated ware as the product of specialists whose skills and access to materials gave them a distinct, valued role among their neighbors.

A century-old question and what it leaves open

Tampa Bay belonged to the Safety Harbor culture, whose largest village was home to the Tocobaga, with smaller chiefdoms including the Mocoso, Pohoy and Uzita. Those communities built flat-topped mounds but, as the overview of the Safety Harbor culture records, were influenced by Mississippian ways without adopting maize farming or becoming Mississippian themselves. They lived mainly from fishing and marine resources.

Whether that influence came from trade, imitation or actual people moving south has long been unsettled. Wallis described it as an open debate for a century. The museum’s account is careful on the point: only some Mississippian traditions took hold around the bay, and the extent of the connection between the two regions remains debated.

The sample is small, and the museum release does not name the individual sites the sherds came from or say how many were decorated, so the 80% figure should be read as a finding about this set. What the grog and mica add is a physical trail, the kind of evidence that can be tested against other collections from the bay and from the Panhandle. Until that comparison is made, the migrant-potter reading stays the researchers’ interpretation of the temper, offered as the best fit for the chemistry, the mineral and the construction methods, and not as a settled account of every household that lived on the shore.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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