Tamara Thomsen has spent three decades diving and documenting shipwrecks in the Great Lakes, the coastal waters off North Carolina, and Canada’s Bay of St. Lawrence.
She helped study the Civil War ironclad U.S.S. Monitor in its watery grave off Cape Hatteras in 2000. She also dived on the wreck of the RMS Empress of Ireland, swimming among the skulls and skeletons of crewmen and passengers entombed in the ship since 1914.
Thomsen has also put 58 shipwreck sites into the National Register of Historic Places, and in 2011, served as team leader for the RMS Titanic’s 100th anniversary survey project by the Woods Hole Oceanographic Institution.
But when asked about the most memorable work of her career, and the “Holy shit!” moment that made it so, the Wisconsin Historical Society’s (WHS) state underwater archaeologist said it began in June 2021 with some old wood she found on the bottom of Lake Mendota, just a half-mile east of her lakeside home in Madison. Three years later, that incidental find climaxed with the documentation of at least 10 ancient dugout canoes in the surrounding sand and marl of the 9,740-acre lake.
Accidental Archaeology
Thomsen’s landmark dive that June morning three years ago was “mostly for fun.” After anchoring her dive-boat among the sailboats moored offshore of John C. McKenna Park, Thomsen splashed into the water and set off. After steering her underwater “scooter” into the depths, she saw what looked like the end of a log embedded in Mendota’s bottom 25 feet down.
The partially exposed “log” probably wouldn’t have drawn a second glance from most recreational divers, but maritime archaeologists are never really off the clock. Thomsen moved closer and studied it through her dive-mask. She soon felt confident the wood was fashioned by human hands, and the log was a dugout canoe
Thomsen surfaced and shared the news with her friend in the boat, Mallory Dragt. Thomsen’s scuba tank was low on air, and Dragt had afternoon plans, so they returned to shore. Thomsen called her colleague Amy Rosebrough, now the state archaeologist for the WHS, and persuaded her to set aside her office homework and join her on the water for a closer inspection and second opinion.
Once onsite, they agreed it was a dugout canoe. Though surprised, Thomsen still wasn’t wowed. For all she knew, the dugout was simply an abandoned Boy Scouts project from the 1950s. Still, they brought a chunk to the surface and then to the USDA’s forest products laboratory in Madison for radiocarbon-dating tests.
Those tests showed the dugout was 1,200 years old and carved from a white-oak log. That placed the dugout’s origins in southern Wisconsin’s “Woodland Tradition” period, which spanned roughly 500 B.C. to the 1200s. That meant the dugout was likely made by the native Americans who built effigy and burial mounds on bluffs farther east above Lake Mendota.
Thomsen knew then she had opened a historical window dwarfing her previous work. This was a career achievement on an already extraordinary resume that includes induction into the Women Divers Hall of Fame 2014, and project leader on exploratory dives deep into flooded caves in Missouri’s Ozarks and southern Wisconsin’s lead and steel mines.
The dugout’s builders were ancestors of Wisconsin’s Ho-Chunk Nation. These people, formerly called the Winnebago tribe, carved the canoe about A.D. 850, roughly 800 years before French explorer Jean Nicolet became the first European to reach Wisconsin. In fact, the canoe’s carvers lived 1,000 years before Eben and Rosaline Peck became Madison’s first white settlers in 1837. In contrast, only 187 years separated Thomsen’s dive from the Pecks’ arrival in what became the state capital and home to the University of Wisconsin.
Knapped Net Weights
The dugout’s floor also held a cluster of five rocks, which hadn’t simply washed in over the canoe’s shallow sides. Rosebrough noticed slight notches in the rocks, which she recognized as knapping by tribal fishermen to make net weights. Once knapped, the rocks were wedged between the fish-net’s strands, which were made from grasses, flaxes, or other fibrous plant materials. Those nets, of course, had long rotted away.
In late October 2021, four months after finding the dugout, Thomsen and other WHS divers excavated the dugout from Mendota’s bottom. A few days later, after rigging flotation bags beneath the dugout, they raised the dugout to the surface on Nov. 2 and brought it ashore with help from Dane County sheriff’s department divers.
Even then, Thomsen assumed the dugout was a “one-off” to add to the Wisconsin Dugout Canoe Survey Project, a statewide inventory of dugouts she is building with archaeology Professor Sissel Schroeder at UW-Madison.
In Spring 2022, Thomsen returned to the McKenna Park mooring field to resume her search, and possibly learn if her find had been a fluke or a beginning. In May 2022, she found a second dugout about 100 yards from where she found the first.
Thomsen could now say, “Holy shit!” with reverence. Two dugouts so close together meant she had likely discovered evidence of an ancient lakeshore village, inhabited when the lake was 20 feet shallower than today. Thomsen said she found the canoes along the edge of a slowly descending bottom, just before it plunges to 40-foot depths.
She said the region’s climate was drier 1,000 years ago, and Mendota’s ancient shoreline likely receded farther during prolonged droughts. In fact, geological records from 6,000 to 12,000 years ago indicate the Yahara River, which enters Lake Mendota on its northern tip and departs from its southeastern corner, sometimes dried up and stopped flowing.
In September 2022, four months after Thomsen found “canoe No. 2,” the WHS announced the discovery when archaeologists and a team of skilled volunteer divers brought it ashore, generating another wave of international attention. Tests on wood samples revealed this second canoe was made from an ash tree about 3,000 years ago, or roughly 600 to 1,000 B.C., making it the oldest dugout ever found in the Great Lakes region by 18 centuries.
Archaeologists theorized that the ancient people cached their dugouts in about 5 feet of water each autumn to protect them from freezing, cracking, and splitting over winter. However, given a hole in the first canoe’s bottom, it’s possible it simply sunk and the owners abandoned it. Either way, the dugout’s owners likely moved inland each fall to more sheltered areas and, for whatever reason, never put these dugouts back into service.
Full-Time Fun
With two ancient dugouts to her credit, Thomsen had even more explaining and story retelling to do as news outlets came calling. She truly hadn’t been hunting ancient history when diving among Mendota’s anchored sailboats and finding the first dugout.
Yes, Thomsen had spent two decades as a respected underwater archaeologist, but her profession evolved from her love of scuba diving, not vice versa. She graduated college in 1991 with a bachelor’s degree in horticulture and agronomy, and in 1993 earned a master’s degree in genetics. But in 1994, she opened her Diversions Scuba dive shop and diving school in Madison, 10 years before the state historical society hired her as its underwater archaeologist and historic preservation specialist.
No matter her job or duties, Thomsen devoted much of her free time to scuba diving, routinely exploring lake bottoms and underwater caves not far from home. And that’s why she and Dragt went diving off McKenna Park that morning in June 2021, just down Mendota’s southwestern shoreline from the home her grandfather built.
Why McKenna Park? Had she heard rumors of possible native American relics around the park or just offshore? After all, what about those burial and effigy mounds to the east, long studied by Rosebrough, her WHS colleague?
No. Being a longtime local, Thomsen just viewed the park as a safe, convenient place to dive because of its “mooring field” about 100 yards offshore. Sailboats tie off there through spring and summer, their mooring lines snapped to large buoys linked by cables to heavy anchors 25 feet below. All those buoys and sailboats serve as obstacles, providing a haven for divers and fishermen from tubers, jet-skiers, water-skiers, wake-boaters, and speeding motorboaters — some of whom ignore or overlook dive flags and no-wake buoys.
Ironic Convenience
Thomsen’s usual swag from such dives includes lost anchors and fishing lures, an occasional spinning rod, rarely a tackle box, and usually bottles, beer and soft-drink cans, and other trash.
But finding those two ancient dugout canoes made McKenna Park’s mooring field an accidental archaeological site; a watery example of “streetlight effect” research. The “streetlight effect” concept comes from a joke about a policeman who helped a man look for his lost car keys beneath a streetlight across the road from his car. After failing to find the keys, the cop asked the man why he wasn’t searching by his car. The man replied, “Because the light is brighter over here.”
In Thomsen’s case, the wave action of motorboats and wake-boats turning to avoid the mooring field might have had an ironic, coincidental impact. Waves from those turning boats possibly disturbed enough bottom sediments to reveal the dugouts.
Thomsen mentioned yet another irony: While the mooring station creates quiet, inviting waters for anglers and divers, those folks inadvertently damaged the dugouts below when dropping their anchors to fish or explore.
“I’m not pointing fingers, because I’ve dropped my anchor in there plenty of times, and might have caused some damage, too,” Thomsen told MeatEater. “But there’s no doubt boat anchors did some damage. Canoe 2 (found in May 2022) was broken and suffered anchor damage. We found a couple of places where an anchor tine dug into it.”
Ironic or coincidental, Thomsen’s discoveries launched extensive, scientifically coordinated searches over the next 20 months, not only by scuba divers but also by Ho-Chunk historians using ground-penetrating radar from atop Mendota’s ice in winter 2023. And in mid-May this year, after finding and analyzing results from those searches, the Wisconsin Historical Society announced the biggest news yet from that mooring field:
Archaeologists had located at least eight, and possibly nine, more submerged dugouts in an area roughly 800 feet long. Radiocarbon-dating tests of wood samples revealed the youngest dugout was about 800 years old and the oldest 4,500 years—yet another record-age for dugouts of the Great Lakes region.
The three oldest dugouts—3,500 to 4,500 years—were made from elm logs, and the youngest dugout (800 years) was made from a red oak log. Also, a 2,000-year-old dugout was made from cottonwood, and four to five dugouts (1,000 to 1,800 years) were made from white oak.
Why all the Hardwoods?
The archaeologists were mildly surprised that 10 out of 11 of the Mendota dugouts were built from hardwoods. Although cottonwood is a hardwood, its wood is relatively soft, more like the softwood logs from pine, spruce, and hemlock trees used for dugouts from northern Wisconsin and elsewhere.
Professor Schroeder said UW-Madison’s statewide dugout canoe survey—which excludes birchbark canoes—has found 101 dugouts since former student Ryan Smazal started crisscrossing Wisconsin in 2018 to document dugouts for his senior thesis. Schroeder said about two-thirds of the state’s dugouts were built from softwoods. The rest were built from elm, ash, hickory, butternut, cottonwood, white oak, and red oak. In contrast, of 174 eastern North American dugouts identified by wood species, Schroeder said 92% were made from softwoods.
So why are the Mendota dugouts made exclusively of hardwoods? “They used what was available where they lived,” Schroeder told MeatEater. “Why else would anyone hollow out an elm log? It was probably the only straight log they had at the time. Details like that tell us a lot about the climate, forests, and habitats where they lived during a given time.”
Straight logs from red or white oaks probably grew in crowded woods, where oaks won’t sprout many branches until growing tall. Elm and ash, however, grow consistently straight with few lower limbs. As foresters say, those species grow tall and straight “unless they have no other choice.”
The only state to document more dugouts than Wisconsin is Florida, with over 400 dugouts on record, including 101 cached along the shorelines of Newnans Lake near Gainesville in 2000. The oldest canoe from the Newnans Lake cache dates back 5,000 years, and the earliest Florida dugout is nearly 7,000 years old. Schroeder said the world’s oldest dugouts were found in Japan, roughly 7,500 years old, and France, 9,000 years old.
When Smazal started his Wisconsin survey in 2018, the state had only 11 known dugouts. Smazal’s travels quickly built the inventory to 34 dugouts. Thomsen and Schroeder continued that work after 2020’s Covid-19 lockdowns. To compile the inventory, researchers scan, measure, and photograph each dugout using iPhones with LiDAR (Light Detection and Ranging) scanning technology. After processing the images and data through photogrammetry software, they can create 3-D models of the dugouts for viewing with virtual-reality glasses.
Most Wisconsin dugouts range from 16 to 21 feet long and 22 inches wide, with the smallest measuring about 7.5 feet in length and the longest nearly 50 feet. Schroeder said the big one was probably built by Lake Superior voyageurs during the fur trade era of the 1650s to 1850s. Shorter dugouts were likely used on oxbows and small lakes and the longer ones on rivers and large lakes.
Now five years into the project, Wisconsin researchers keep locating dugouts by reading newspaper archives, and visiting rural and small-town libraries, museums, historical societies, old barns and garages, and Smithsonian collections. The inventory also includes a dugout found in the garage attic at a state park, and three from the Ho-Chunk people, and four from the Menominee Nation.
Universal Traits
Thomsen readily credits Smazal for helping her recognize the first dugout in Mendota. She said she had studied so many of his dugout photos the previous three years that she recognized telling details in the “log” at McKenna Park.
In fact, dugout canoes worldwide share many similarities in size, design, length, and construction techniques. Schroeder said no Wisconsin dugout has oar stations, all had flat bottoms, and most have low sides. In fact, Thomsen said the Mendota dugouts more closely resemble modern paddleboards than modern canoes. “They could have poled or paddled them with their legs hanging over the sides,” she said.
Then again, how many ways could anyone of any era shape and hollow out logs to create functional watercraft? Whether the builders used fire, clam shells, stone awls, a Dalton adze (stone scraper), stone axes, steel hatchets, steel chisels, or long-handled claw hammers, their finished dugouts from the Great Lakes look much like dugouts built in Florida or the Solomon Islands of the South Pacific.
And building a dugout, even in more modern times with steel tools, seldom goes fast. The 1961 book “PT-109: John F. Kennedy in World War II” by Robert Donovan details how native islanders paddled dugout canoes to rescue the future president and his surviving crew from an island after a Japanese destroyer rammed and sank their boat on a dark, moonless night in August 1943.
Donovan said the islanders carved dugouts from hardwoods, writing: “Dugout canoes are thick, sturdy craft, hewn with an adze from the trunk of a single tree, preferably a goliti tree. When the natives set out to make a canoe they put a coconut on a stick nearby, and traditionally the job is supposed to be finished when the coconut sprouts in two months.”
Sixty years later, the goliti tree, a hardwood, is still considered the only “truly good tree for making dugout canoes” in the Solomon Islands.
Meanwhile, research continues at Mendota’s dugout site, and on the 10 to 11 dugouts already found. The archaeologists want to pin down whether they found eight or nine dugouts in their follow-up searches the past two years. Because each dugout is fashioned from individual logs, radiocarbon-dating tests and strontium-isotope analysis of wood samples—roughly of football to basketball size—should reveal if the canoe(s) came from one or two tree species, or perhaps one species growing in different eras or different regions.
The Mendota dugouts found since 2022 won’t be brought ashore. They remain where they were found, largely out of respect for their ancestral builders, but also because researchers think they’ll learn everything necessary from samples already ashore.
Conclusion
And what about the two dugouts Thomsen found in 2021 and 2022? Both remain secured in storage at the Historical Society’s state archives facility in Madison. Both dugouts began a preservation process in February 2024 that uses polyethylene glycol, or PEG, to stabilize the wood. The treatment is expected to conclude in 2026.
The dugouts will then be sent to Texas A&M University to be freeze-dried, so they’re stable and solid for public display. The dugouts and stories about their ancient builders will be shared when the new Wisconsin History Center opens in 2027.
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