Ancient Native Americans living in Florida made use of lethally toxic fish for mysterious purposes, a study reports.
Recent archaeological investigations at the Mound Key site in southwestern Florida—associated with the Indigenous Calusa people—have identified "unique" deposits containing an "unprecedented" number of porcupine fish and burrfish (hereafter referred to collectively as burrfishes) remains.
These fish contain a toxic compound that can be fatal to humans if ingested. In a study published in the Journal of Anthropological Archaeology, a researcher proposed that burrfishes' remains at Mound Key likely represent specialized production and use of a toxic resource for non-food purposes that has not previously been identified in the U.S. Southeast.
The exact purpose the burrfishes served for the Calusa people has yet to be determined, according to study author Isabelle Holland-Lulewicz with the Department of Anthropology at Pennsylvania State University. The latest research helps to shed light on the lifestyle and economic activities of this ancient native American group.
The Calusa culture, native to the coastal areas of southwest Florida, was a complex fisher-hunter-gatherer society that is believed to have emerged around A.D. 500. The culture developed from the archaic people of the Everglades region who had inhabited the area for thousands of years.
The Calusa became particularly dominant in the region by the time of contact with the Spanish in the 16th century. The culture is known for its complex social structure, mound-building and sophisticated use of the resources found in the local environment, which included coastline, estuaries and small islands, that enabled the group to thrive without relying on agriculture.
By the late 18th century, though, the Calusa had effectively been wiped out due to a combination of factors, including diseases introduced by Europeans, against which they had no immunity, as well as conflict with colonizers and other indigenous groups.
One of the most important sites associated with the Calusa is Mound Key, a 51-hectare man-made island in modern-day Estero Bay, southwest Florida.
Mound Key Island in Florida was developed over many centuries by the Calusa and their ancestors via the systematic deposition and layering of shells, fish bones, and other refuse from daily activities, such as food consumption and tool-making.
These mounds grew over time as the Calusa continued to inhabit and use the area, effectively elevating the land above the surrounding waters of Estero Bay.
This human-engineered island—whose occupation spans from around A.D. 500 through Spanish contact to the 17th century—eventually became the political and ceremonial center of the Calusa kingdom by the beginning of the colonial era.
It features a complex layout of refuse mounds, canals, causeways, burial mounds and watercourts—structures thought to have been used by the Calusa for capturing and storing live marine animals, like fish, until they were needed for consumption.
Archaeological research at Mound Key has identified several deposits rich in burrfishes, which date to between roughly A.D. 1000 and A.D. 1600. These fish are common in both the marine and brackish waters of the Gulf of Mexico.
Among their notable characteristics, these fish have a parrot-like beak and can inflate their bodies by swallowing mouthfuls of water as a defense mechanism against predators. They also feature another defense mechanism: sharp spines radiating outward from the skin when the fish is inflated.
Generally, burrfishes are not deemed valuable or desirable food sources—at least in the Western world. Firstly, these fish consist of very little meat other than innards. Secondly, they—along with other relatives in the order Tetraodontiformes—contain a compound known as tetrodotoxin that has the potential to kill a human within an hour of consumption.
The toxin acts on both the central and peripheral nervous systems and can cause numbness, increasing stages of paralysis, gastrointestinal distress and respiratory failure. It can be found in the gonads, skin, liver and/or intestines of fish in the Tetraodontiformes group.
Burrfishes are commonly found in archaeological assemblages from varying contexts across the southeastern United States, Latin America and the Caribbean. However, the numbers of recovered burrfishes tend to be low. The site of Mound Key in southwestern Florida proves to be an exception, featuring an "unprecedented" number of individuals in highly localized deposits.
Intriguingly, no spines have been identified among all the remains of burrfishes recovered at Mound Key, with the animals represented primarily by beaks. This pattern is the reverse of most deposits containing burrfishes found at other sites across the U.S., Latin America and the Caribbean, where spines make up most of the remains.
Given the physiological characteristics of burrfishes, including the presence of the potentially lethal tetrodotoxin, as well as archaeological evidence from the Mound Key site, Holland-Lulewicz proposes that the Calusa engaged in an economy centered on the production of some kind of non-food product that was likely made from the spines, skins and/or innards of these creatures.
"While the global ethnographic record contains references to conspicuous uses of burrfishes, like the Melanesian war helmets, such highly visible uses would have likely been included in Spanish descriptions of the Calusa, but none have been identified to date," Holland-Lulewicz wrote in the study.
"Others have suggested use of spines for bloodletting practices, though they could have also been used in tattoo kits, as arrow or spear points, or for any number of other uses. The Calusa could have utilized the properties of the tetrodotoxin in medicinal, ritual, or even military contexts but again evidence for such use has not been identified."
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Reference
Holland-Lulewicz, I. (2024). Beyond Subsistence: Toxic burrfishes and non-food-based economies among the Calusa complex fisher-hunter-gatherers of the American Southeast. Journal of Anthropological Archaeology, 77, 101653. https://doi.org/10.1016/j.jaa.2024.101653
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