Jessi Halligan stares at a laptop screen on the deck of a 50-foot vessel, a few miles from the Canadian border in the middle of Lake Erie.
On screen is a stack of squiggly colored lines that are indecipherable to the untrained eye. But to Halligan, an underwater archaeologist at Texas A&M University, they’re clues, showing where to dig for evidence of people who lived here some 12,000 years ago.
At that time, at the end of the last Ice Age, the climate of Erie, Pennsylvania, was roughly that of Alaska today, and this part of the lake was dry land.
That’s why Halligan and her collaborators think that under the water are ancient plants, trees, tools, and remnants of an old world that the earliest Americans inhabited. But to find what they’re looking for, they have to figure out where to look.
Halligan points to the screen at a series of blue lines. These are sonar readings that indicate different layers of the lake bottom.
“This is layered sands, gravels, and muds that have survived after the glaciers have come and gone,” Halligan said. “So potentially this is an old river system.”
“People would have wanted to be near,” she said. This old riverbed probably does not have the stone and bone tools Native Americans left behind, but they might not be far away.
The needle in the haystack
Halligan and her collaborators are on Lake Erie for a three-week field research session, as part of a long-term study. The research is twofold: they scan the bottom for promising sites to search for artifacts, then they do some digging.
“It’s sort of finding the haystack and then making the haystack smaller and smaller,” says Ben Ford, an archaeologist at Indiana University of Pennsylvania who is one of the study’s co-directors, along with Halligan and David L. George-Shongo Jr., director of the Seneca Nation of Indians Tribal Historic Preservation Office.
The team is focused on an underwater ridge left behind when the glaciers retreated. It was land, with water on both sides.
“It would have been a relatively good place to live,” said Ford. “You’ve got lakes nearby and rivers nearby; animals probably would have traveled along it.”
In a few days, the team will don scuba gear and dive 60 feet down to the lake bottom, where they will take samples of the lake bed by pounding tubes into the sediment, then analyze what they find.
The divers have to work fast, because they can quickly use up their limited air supply by exerting themselves as they drive the cores into the lake bottom.
Looking for ancient life, underwater
The field of underwater archaeology has yielded intriguing finds, especially with advances in underwater sensing and other technologies. Halligan said if we don’t look underwater, we are only getting part of the picture of the human experience.
Well-known underwater sites include Atlit Yam, a drowned settlement off the coast of what is now Israel, a 7,000-year-old wall off the coast of Brittany in France and a stone structure in the Baltic Sea near Germany dating back 11,000 years.
Underwater archaeological sites tend to be better preserved than sites on land, said Halligan, who is associate professor of anthropology at Texas A&M and associate director of the Center for the Study of the First Americans.
Organic materials like bone, wood and leather degrade slowly underwater. They are spared the damage from freeze-thaw and the soaking-and-drying cycles that objects on land face. If they’re buried in mud, they are protected from the degrading effects of oxygen and light.
“Everywhere people have looked, they’ve found a few places where there are preserved things left behind,” Halligan said. “When we look, we find things.”
Going underwater is also the only way to find some types of human settlements. As the polar ice caps melted at the end of the Ice Age, oceans rose, drowning countless sites around the globe.
“There are no coastlines left anywhere in the world from 12,000 years ago, 13,000, 14,000 that are not now underwater,” said Halligan, who grew up on a South Dakota cattle ranch. After learning about the discovery of King Tutankhamun’s tomb in the fifth grade, she knew she wanted to be an archaeologist.
Three years into the Lake Erie study, the team found promising results.
Last year, they pulled a preserved twig from an Ice Age-era conifer tree from about six feet of sediment from the lake floor. They carbon-dated the twig to 12,300 years ago. This proved that the surrounding sediment dated to around that same time period.
“It was just a small twig that had been buried by mud … and stayed buried for 12,300 years. You pull it out, and it looks exactly like any twig you’d find falling off a tree nowadays,” says Nick Bentley, a Ph.D. student at Texas A&M who is part of the research team. “It didn’t decay or decompose whatsoever.”
Answering questions about the earliest Americans
Their research could help answer some big questions about humanity’s entry into the Americas. Archaeologists have long believed that hunter-gatherers crossed over the Bering Strait into the Americas 14,000 years ago.
Some scientists theorize people have been in the Americas for much longer. Halligan herself is excavating a site in Florida dating back 14,500 years.
Native American groups, like the Seneca Nation of Indians in modern-day Western New York, say their ancestors have always been in North America.
A group of archaeologists working in Lake Huron in Michigan found intact ‘caribou lines’ — stone markers laid out by ancient hunters to steer migrating herds to favorable hunting spots.
“We hypothesized that this would’ve been a natural corridor for caribou migration, and that hunters would have adopted techniques like they do in the Arctic today of building various kinds of drive lines and blinds to ambush caribou during their migrations,” said John O’Shea, an archaeologist at the University of Michigan and one of the lead researchers on the Lake Huron project.
“They’re pretty much just the way they were left. In some cases, we still have stacked stones,” O’Shea said. They also found 9,000-year-old flakes of obsidian, volcanic glass used for arrowheads and tools, that have been sourced to eastern Oregon, 2,500 miles away. It provided proof that the Americans of the end of the Ice Age had long-distance travel networks.
A changing climate, then and now
The researchers said studying these drowned worlds could help us better understand our own era of climate change. At the end of the Ice Age, seas were rising, and ecosystems were shifting.
“We are very interested in seeing how people adapted to their changing environments,” said Trevor Gittelhough, a Texas A&M Ph.D. student with the team. “How did they adapt to sea level rises, which is something that we are dealing with today. There’s that tie-in between us today…and the people who were living here 14,000 years ago.”
Halligan said the search for underwater sites is important because they teach us what other humans went through at a period of dramatic change.
“It could really tell us a lot about what some of the very early Indigenous people in this area, as the glaciers are coming off, what they lived like, who they were, what their lives were like,” she said.
At the end of a long day on the water, Halligan and her team packed up their laptops, pulled in their sonar equipment, and headed to shore. They planned to comb through the data and decide where to plan their next lake floor dig.
In the next few days, they will be back on the lake, pulling up core samples to study— a look back at our ancient past, when the climate, and the world, were much different than they are today.
