What Lies Beneath

Scuba divers explore the bottom of Lake Huron for ancient archaeological sites. Photo: Tane Casserley/NOAA

By Alex Piazza
apiazza@umich.edu

Fifty miles off the shore of a northern Michigan town, John O’Shea and his crew lowered a sonar device 120 feet beneath Lake Huron in search of ancient landmarks.

The process has become somewhat routine for O’Shea, who has explored the Great Lakes for more than three decades.

“For us, archaeology is a long, grinding accumulation of information,” said O’Shea, Emerson F. Greenman Collegiate Professor of Anthropological Archaeology at the University of Michigan. “You very rarely get an ‘aha moment’ where something appears right beneath you.”

On this particular day, however, O’Shea and his crew experienced their ‘aha moment’ when sonar revealed a 9,000-year-old caribou hunting structure hidden along the lake bottom.

“We just sat there with our mouths wide open because this is what it looks like in the movies,” said O’Shea, also curator of Great Lakes Archaeology at the U-M Museum of Anthropological Archaeology, who monitored underwater footage aboard his boat. “It almost never works this way in practice. Holy cow. It was just mind blowing.”

This summer, with funding from the National Science Foundation, researchers will explore the Great Lakes in search of more ancient archaeological sites. Beyond its historical relevance, their underwater discoveries yield unprecedented insight into important issues like climate change.

“What excites us is the fact that our approach not only has a tangible impact on the Great Lakes community, but it also provides us an opportunity to predict the future impact of environmental change,” said Robert Reynolds, visiting associate research scientist at the U-M archaeology museum. “We view this work as a major contribution to our future.”

History reconstructed

Their discovery dates back 9,000 years, when an 80-mile land bridge connected northeast Michigan to southern Ontario.

The land bridge, which today is buried 100 feet beneath Lake Huron, attracted hunters who manipulated the environment to lure in caribou.

One of the quirks among caribou is their propensity to follow linear patterns, so once hunters picked up on this behavior, they used it to their advantage. Hunters would line rocks up in a row to channel the movement of animals toward their hunting blinds.

These behavioral clues, in part, helped researchers locate the most complex hunting structure beneath the Great Lakes.

O’Shea and his team started with underwater depth data from the National Oceanic and Atmospheric Administration (NOAA) to identify sections of the lake bottom that mirrored the ideal landscape for hunting caribou.

But the Great Lakes are vast, comprising nearly 95,000 square miles, so O’Shea teamed with Reynolds, an artificial intelligence expert with experience simulating ancient landscapes.

Reynolds, who also is a computer science professor at Wayne State University, used the NOAA data, along with environmental evidence collected from the lake bottom, to build a 3-D virtual world that depicted what the land bridge would have looked like around 10,000 B.C.

His research group also produced models of intelligent caribou group behavior using a machine-learning tool, which helped predict optimal migration paths along the land bridge.

This information from the 3-D world allowed O’Shea and his crew to pinpoint specific locations along Lake Huron, including the spot 50 miles off the coast of Alpena, Mich. where researchers discovered the historic caribou hunting structure.

“You’re basically looking for a needle in a haystack,” said Ashley Lemke, a former U-M doctoral student who first discovered the ancient hunting structure on the boat monitor. “This was just one of those beautiful, everything comes together-type moments.”

Scuba divers collected sediment samples from the lake bottom, some of which yielded remnants of ancient artifacts that helped researchers understand how people once used that site. Researchers also took photos and recorded video of the lake bottom to document their historic discovery.

“We had all worked on this project for so long, so we felt really vindicated after finding this site,” said Lemke, now an assistant professor of anthropology at the University of Texas at Arlington, who plans to use similar research methods to study underwater sites near North Carolina and the Gulf of Mexico.

Virtual worlds

What was the environment like in Michigan 9,000 years ago when hunters chased down caribou?

Reynolds began working with O’Shea solely to help discover ancient landmarks buried beneath the Great Lakes, but the objective behind his 3-D world has since expanded.

Reynolds uploaded the 3-D world to an online game development platform so that users can experience what prehistoric life was like. Researchers expanded the virtual world so that users can walk along the 80-mile land bridge, which is outfitted with virtual caribou, vegetation, hunting blinds, lakes and streams.

“Our goal was to build a 3-D world that literally characterized what the land bridge would have looked like around 9,000 B.C.,” he said. “With some slight modifications, we can use this virtual world to study how changes in lake levels impacted the surrounding coastline and affected the behavior of ancient people.”

Researchers soon hope to introduce the 3-D world to current Alaskan caribou hunters so they can visualize what hunting was like 9,000 years ago. Traditional hunters also could help researchers identify locations beneath the Great Lakes that may have housed ancient hunting structures or campsites.

“We’re doing this as part of an archaeological project, but we also see great potential for using this 3-D world beyond just studying the past, and instead focusing on the future,” Reynolds said. “As lake levels rose, some of these early hunting sites turned into fishing sites, which goes to show how fluctuating water levels have impacted society over the years. This technology allows us to gain a better understanding of how people adapted to climate change, which has great benefits for society moving forward.”

Meanwhile, O’Shea never anticipated his research to appear in videogame format, but the addition of artificial intelligence allows him to further explore environmental change.

“Archaeology is normally a backward-looking discipline, but this is a case where we can do some good in the modern world, and maybe even provide some models to help manage caribou herds or investigate climate change,” O’Shea said.