Below the surfaces of freshwater springs, lakes and rivers, sunken landscapes hold clues about the daily lives, beliefs and diets of the first humans to settle in what is now the United States. But submerged prehistory, as the study of these millennia-old sites is widely known, is often overlooked in favor of more traditional underwater archaeology centered on shipwrecks.
“There’s tremendous work to be done,” says Barbara Purdy, author of The Art and Archaeology of Florida’s Wetlands and an emeritus anthropologist at the University of Florida. “Fast-developing technology holds great potential to explore what lies below. One day, the sunken world will unlock the answer to how America was really settled and how [our] ancestors lived.”
From Miami to Lake Huron to Warm Mineral Springs, these are three sites driving the conversation about the nascent discipline.
Warm Mineral Springs
The hunt for sunken evidence of early humans in North America began some 60 years ago with a swirl of controversy in southwestern Florida. In 1959, retired Air Force Lieutenant Colonel William R. Royal uncovered traces of prehistoric people while diving at Warm Mineral Springs, an hourglass-shaped sinkhole formed when an earthquake collapsed a subsurface cave around 20,000 years ago. Because Royal was “an untrained amateur,” says Purdy, “scientists poured cold water over his bold claims.”
The spring’s main claim to fame is its association with Spanish conquistador Juan Ponce de León, who supposedly identified it as the Fountain of Youth in 1513. Though tales of the explorer’s search have been greatly exaggerated, hordes of modern water worshippers have followed in his wake. “Few who take the waters can deny their healing properties and therapeutic nature,” says Sarasota County Archaeologist Steve Koski.
Royal was the first to dive in the sinkhole, which has a surface circumference of 1.4 acres and reaches depths of up to 250 feet at its center. In January 1959, he spotted stalactites some 70 feet below the water’s surface, in a cave off the main basin.
Limestone formations grown over thousands of years, stalactites typically don’t form underwater. According to a geologist consulted by Royal, the last time the sea level was low enough for such structures to form in the cave was 6,000 years ago. On his next dive, Royal discovered a human thighbone on a ledge near the cave, suggesting it dated to around that same era—well before humans had been believed to have arrived in Florida around 3,500 years ago.
Royal “knew [he] had found something that would turn archaeological thinking around,” pushing humans’ presence in the region back by thousands of years, he told Florida magazine in 1987. But the establishment refused to listen to him, even after he uncovered additional human remains, as well as the bones of extinct giant sloths, saber-toothed tigers and camels.
In the summer of 1959, Royal recovered an intact human skull at a depth of about 45 feet. Examining the bones, he noticed what felt like a “soft and slimy soap” at the base of the skull. Royal was convinced it was millennia-old brain tissue—an improbable theory given how quickly brains tend to decompose after death but one that would ultimately prove correct.
The discovery happened to be filmed by an NBC crew that caught wind of the project. But scholars shrugged, concluding the story must have been a made-for-TV stunt. In the lab, skeptical scientists raised their eyebrows, too. The brain was as fresh as if its owner had just died. Though wood found in the same sediment as the skull was later radiocarbon dated to 10,000 years ago, Royal and his main collaborator, marine biologist Eugenie Clark, continued to be lambasted by the press. As Clark later recalled, naysayers told the pair to “stick to the fishes.”
Seven years after the brain’s discovery, an independent radiocarbon analysis conducted in Monaco dated the skeleton to between 7,140 and 7,580 years ago. Subsequent studies indicated the brain belonged to a 5-foot-6, 19-year-old woman with a dietary deficiency. “Indisputable proof followed in 1973 when, under 1930s Coca Cola bottles and a 78-rpm phonograph record, Wilburn ‘Sonny’ Cockrell, Florida State’s underwater archaeologist, excavated an entire human skeleton,” says Purdy. The new Warm Mineral Springs find “dated to more than 11,900 … years ago, making it the oldest human remains in the Western Hemisphere.”
Lake Stanley and Lake Huron
Over 1,200 miles north of the Sunshine State, John O’Shea, an anthropologist and curator at the University of Michigan’s Museum of Anthropological Archaeology, has spent a large part of his life investigating Lake Huron. Around 10,000 years ago, the basin now occupied by Lake Huron was home to another freshwater lake whose water level was 300 feet lower than Huron is today. The submerged lake, which boasted waterfalls as large as Niagara Falls, is known as Lake Stanley after the geologist George Stanley, who found evidence of its existence in the 1930s.
In the 2000s, O’Shea had a hunch that somewhere below Lake Huron stretched a lost prehistoric land. But he wasn’t sure where to begin his search of the lake basin. Caribou—the main food source for the area’s prehistoric peoples—proved to be the key to unlocking Lake Stanley’s chilly, dry landscape, which was once dotted with spruce trees, sedge and sphagnum moss.
For early humans with limited resources, hunting caribou was a necessary pursuit. People could eat their meat, use their sinews as thread, turn their hides into clothing and tents, and make weapons or tools out of their antlers and bones.
Studies of caribou migration patterns in Alaska suggest the animals obsessively follow the same routes seasonally. Armed with knowledge of these paths, “modern caribou hunters create lines out of rock and brush to channel the animals into kill locations,” O’Shea says. He and his colleagues brought in Robert Reynolds, an expert on artificial intelligence and group decision-making at Wayne State University, to gauge whether prehistoric hunters used a similar strategy.
The team focused on the Alpena-Amberley Ridge, a ten-mile-wide land bridge that linked northern Michigan with central Ontario, crossing modern-day Lake Huron on the way. “Reynolds and his students designed caribou automata and let them loose on a virtual world simulation map of Lake Huron’s sunken world,” O’Shea says. “Then computers tracked their movements.”
The simulation worked, pinpointing several likely locations for hunting structures across a 27-square-mile area. The researchers mapped the spots—ranging in depth from 39 to 129 feet—with side-scan sonar and autonomous underwater vehicles. They then let loose mini remotely operated vehicles equipped with video cameras. At promising sites, scuba-diving archaeologists photographed and collected soil samples to sieve on land for small finds. Finally, the team revealed a prehistoric hunting master plan.
According to the analysis, early hunters constructed lines of small boulders (measuring up to 1,150 feet in length) to funnel caribou toward “blinds,” 11.5-foot-wide hideouts ringed by five large boulders, some 9,000 years ago. “Pretty simple blinds like these could hide two or three hunters until they were surrounded by the animals,” says O’Shea. The team found two structures where meat was stored during the winter, as well as one stocked with tools.
The Alpena-Amberley Ridge has fossilized the Great Lake’s prehistoric annual life cycle. In the fall, when the caribou’s antlers and meat were in their prime, hunters moved to the ridge to prepare for winter. Families stashed the preserved meat in stone “freezers” on the ridge on Lake Stanley; the hunters braved the frozen lake to remove provisions when they were needed. When spring arrived, the scattered families reunited. The warming months were bad for storing meat long-term, so after hunting, early humans stayed on the ridge, renewing acquaintances and swapping stories of family and survival.
Back in Florida, archaeologists are poring over Miami’s damp black soil. Most of the downtown has been built over and lost to development, leaving pockets of the Miami River shoreline as one of the last chances to reconstruct the city’s earliest history.
When Ponce de León anchored in Biscayne Bay in July 1513, he wrote in his journal that he’d “reached Chequescha”—a reference to the Native American Tequesta tribe. Based in southeastern Florida, the Tequesta lived in the region for some 2,000 years. Around 100 C.E., they established their main village at the confluence of the Miami River and Biscayne Bay.
“A lot of people who grew up in Miami or moved here think this is a modern city,” says Robert S. Carr, director of the Florida-based Archaeological and Historical Conservancy. “They believe it was created from dredge-and-fill operations by the railroad and hotel tycoon Henry Flagler, and before that it was all swamp. But that’s not true.” Archaeological finds made by Carr and other scholars indicate the Tequesta and other local Native American tribes adopted a settled lifestyle.
To date, Carr has investigated 18 ancient sites linked to Miami’s first inhabitants. In 1998, he unearthed traces of a circular structure measuring 38 feet in diameter at the mouth of the Miami River. Cut into limestone bedrock, the 24 holes that make up the Miami Circle served as the foundation of a Tequesta building, perhaps one used for ritual or ceremonial purposes. Analyses of burnt wood and artifacts found at the site suggest it was used between 500 B.C.E. and 900 C.E. The circle is the only known prehistoric structure of its kind built into bedrock in the U.S.
Since 2005, Carr has focused on pockets of the Tequesta village located less than half a mile north of the circle. In 2013, his team uncovered thousands more ancient postholes, some from 11 circular structures cut into the bedrock. Natural freshwater springs that still bubble up from deep underground today would have enticed the Tequesta to settle in the area, Carr says.
Carr thinks the posthole village is the earliest preserved urban plan in eastern North America. Here, several hundred Tequesta lived on platforms in houses raised above the water level by wooden stilts. They docked their canoes on the riverbank under their houses and used wooden boardwalks to cross from one building to the next.
The Tequesta were expert fishers who stretched nets across the Miami River and built barriers to funnel fish into their clutches. They ate gar and manatees, topping up their diet with turtles and alligators. Their hunters paddled canoes into the Everglades, just five miles inland, to catch deer, raccoons, squirrels, reptiles and snakes.
Beyond waterways acting as a key food source, “water was a critical aspect of the Tequesta’s cosmology,” Carr says. “The Tequesta believed there were three souls: one in your shadow, one in your eye and the third your reflection in the water where the soul looked back at you.”
Water was also a key element in Tequesta mortuary practices. The Spanish name for Key West, an island southwest of Miami, was Cayo Hueso, or Bone Cay (a moniker that got lost in translation when the English mislabeled their maps). When Spaniards arrived in the region in the 16th century, they found bones scattered across the beaches.
“They imagined these were remains of victims slain by fierce cannibals and heathens,” Carr says. In truth, however, “they were just part of the mortuary preparations for secondary burials. The bodies were laid out near the water, where they were subject to decomposition and desiccation from buzzards, the weather and time. … This process is all linked to water.”
The Tequesta village on the south bank of the Miami River and nearby Miami Circle may have been the settings for similar ritual acts focused on freshwater. The name Miami is derived from Mayaimi, which translates to “big water” in the Tequesta language.
In 1567, Pedro Menéndez de Avilés, founder of the colony of St. Augustine, convinced the Tequesta to let the Spanish build a fort and Catholic mission at the mouth of the Miami River. Though the Spanish abandoned the mission soon after, European contact—and the violence, disease and enslavement that followed—signaled the end of the Tequesta’s way of life. In the 18th century, the few surviving Tequesta resettled in Cuba.
Preserving sunken prehistory
The potential for studying America’s sunken past is bottomless. Waterways’ oxygen-free environments keep archaeological finds astonishingly well preserved. Wooden artifacts abound in Florida’s freshwater, from 185 canoes dating back 6,050 years to a statue of a seated figure recovered from a lake in Okeechobee County in 1921.
Elsewhere in Florida, researchers are studying a sinkhole in the Aucilla River, south of Tallahassee, that served as a prehistoric watering hole for humans, mastodons, bison, bears and dogs. Dated to at least 12,200 years ago, it’s the earliest documented site of human activity in the southeastern U.S. To the northwest, in Michigan’s Grand Traverse Bay, underwater archaeologist Mark Holley has discovered evidence of a more than one-mile-long line of boulders possibly used to herd caribou. One of the stones features what appears to be a petroglyph of a mastodon. Both sites hold enormous untapped promise. But the future study of submerged prehistory is far from secure.
The city of North Port, owner of Warm Mineral Springs, understandably hopes to cash in on the site’s therapeutic qualities. A plan that would have maintained the spring as a park, with new walking trails, a canopy boardwalk, lookout towers and an event pavilion for weddings, went nowhere after developers estimated the cost at $18 million, twice the $9 million allocated for the restoration. The latest proposal calls for a resort with 300 residential units, a wellness center, a restaurant and a Native American history museum.
Some locals are up in arms over the planned development. An estimated 70 percent of Warm Mineral Springs remains unexplored, including a 148-foot-deep debris cone that likely contains a trove of late Pleistocene megafauna, as well as weighted bundles dropped into the spring during rituals. Construction work could shake the ground so much that this submerged prehistory crumbles away.
“The city has been [a] good steward of the underwater archaeology by restricting diver access,” says archaeologist Koski. “Warm Mineral Springs should not be open for commercial tour dives or access without sound professional academic research. … There is still great potential for research. There are likely more undisturbed human remains … and evidence of activities of the people who visited the site.”
The future for some pockets of the Great Lakes looks far brighter. With support from the National Oceanic and Atmospheric Administration, O’Shea’s team has started mapping more of the Alpena-Amberley Ridge. Submerged offshore areas that were once islands could hold early signs of human activity.
O’Shea says, “The Great Lakes have tremendous potential for expanding our understanding of prehistoric America. There are portions of the archaeological record that simply do not exist anywhere else.”
In Miami, archaeologists working in the shadow of skyscrapers, private marinas and waterfront restaurants must balance the interests of developers with public sentiment and their own quest for knowledge. A dig currently underway in the Brickell neighborhood has uncovered pottery, tools and animal bones associated with the same Tequesta village previously studied by Carr. But representatives from the American Indian Movement and the Miccosukee Tribe of Florida have called for all excavations at the site to stop.
“[I] felt like our ancestors were being disrespected,” Betty Osceola of the Miccosukee Tribe tells Local 10 News.
Though arrow and spear points discovered during the dig appear to date to around 8,000 years ago, Carr says radiocarbon testing places activity in the village between 750 B.C.E. and 1763. He theorizes that the Tequesta people found the prehistoric objects and brought them back home, unwittingly providing an example of ancient curiosity confusing modern archaeology.
As in all great cities, the pace of progress can’t be stopped. The final vacant lot in Brickell is being excavated ahead of construction of new residential buildings. A movie theater already covers the section of the Tequesta village identified by Carr in 2013. A Native American cemetery lies under a Whole Foods in the same vicinity.
Miami Circle has been admirably excavated, but its importance is already fading. The city has no reconstruction of a Tequesta structure, nor a visitor’s center for education and tourism. Today, the circle is mostly used as a dog park.
“Let’s integrate this prehistory into the consciousness of Miami and make it accessible for the public and tourists,” Carr suggests. “That has not happened. It lacks the respect it needs.”