Florida 'circles' may be ancient fisheries.

Florida 'circles' may be ancient fisheries

A mysterious, prehistoric network of circular canals and earthen mounds dotting the landscape of southern Florida's interior may represent North America's earliest known fisheries, says archaeologist Robert S. Carr, who described his ongoing investigation of the sophisticated Indian construction projects to SCIENCE NEWS last week.

Some of the nearly 40 "earthwork" sites -- most discovered by Carr since 1974 -- date to as early as 450 B.C. Others originated at about the time the Spanish explorers reached Florida in the 16th century. The carefully engineered structures indicate that prehistoric hunter-gatherers inhabiting inland regions of southern Florida developed socially stratified societies based on fish harvesting, asserts Carr, who directs the nonprofit Archeological and Historical Conservancy in Miami.

An agricultural way of life is usually considered essential for the nurturing of social classes, but Indians in southern Florida and the Pacific Northwest -- another region where marine resources abound -- broke that rule, he says. Anthropologists have long noted that Indians along Florida's southern coast developed stratified societies with powerful chiefs and shamans although these tribes fished and hunted rather than planting crops. Inland inhabitants probably had a social elite that coordinated construction of fish harvesting sites, Carr maintains.

Other investigators have speculated that Florida's earthworks either served some type of ceremonial purpose or provided drainage ditches for maize fields. But early Spanish accounts contain no mention of agricultural activity in southern Florida. Moreover, researchers have not identified maize pollen at any of the circular canals.

"Carr's new interpretation is a viable alternative theory," says archaeologist John Griffin, retired chief of the National Park Service's Southeast Archaeological Center in Macon, Ga. Indians living along southern Florida's coast were avid fish consumers, Griffin notes, so the construction of numerous inland fisheries "makes sense given the overall regional pattern."

Using aerial photographs, Carr discovered a unique earthwork complex early this year. A rectangular earthen "plaza," 400 feet wide and 200 feet long, dominates the site. Pottery from several large sand mounds near the plaza dates to sometime between A.D. 1200 and A.D. 1600, Carr says.

The earthwork sites more commonly feature circular ditches, some up to 1,450 feet in diameter and 6 feet deep, located in the savannas and floodplains adjacent to Lake Okeechobee and various creeks and rivers. Lake Okeechobee is located in mid-southern Florida. The man-made circles contain strategically placed gaps where drainage canals extend outward, Carr says. At one site, aerial photographs of a large circle show the traces of two pronged channels draining from a nearby river. Another site features a circle with two prongs allowing for the diversion of water from a creek.

The Indians could easily have blocked the channels to trap fish that swam into the ditches, Carr contends. However, evidence confirming his theory -- such as fish bones embedded in the bottom of a ditch -- has not been found.

The circular structures may also have functioned as ceremonial sites, he says. All the circles investigated so far surround earthen mounds, which may have been human burial mounds.

Most of the ditches are near sites of ancient settlements, he adds. They bear some resemblance to 1,700-year-old circular canals in southern Ohio, which scientists attribute to the Hopewell Indian culture, but Carr says the "Hopewellian circles" clearly were used to drain cornfields.

He plans to further investigate the curious earthworks this fall, focusing on a site containing two large canals just west of Lake Okeechobee.