The story of people who hunted caribou in the Great Lakes region 9,000 years ago has been uncovered at the bottom of Lake Huron.

Archeological remains of hunting blinds and other structures built by aboriginal caribou hunters were found underwater 56 kilometres from shore by sonar and dive teams led by University of Michigan Museum of Anthropology archeologist John O'Shea and his colleagues

The elaborate hunting setup suggests that large groups of hunters congregated here and hunted caribou together each spring, the researchers reported in a paper published this week in Proceedings of the National Academy of Sciences.

"For mobile hunters, this is a really valuable time, because they share information, they trade, they have marriages, they do all these things that you only do when you get a critical mass of people together," O'Shea said in a phone interview with CBC News Monday.

"This is, I think, giving us a really unique picture of what that whole annual cycle was that these hunters were following."

The discovery also fills a gap in the archeological record, O'Shea said.

Lake levels 100 metres lower

At the time the hunters lived, the glaciers were retreating and water levels in the Great Lakes were as much as 100 metres lower than they are today. Lowlands tend to be richer hunting grounds, which means that most of the areas that people lived at that time are now underwater.

The hunting blinds found at the bottom of Lake Huron were V-shaped, consisting of a large rock and smaller rocks on either side. A hunter could crouch and hide behind them. (Courtesy of John O’Shea/UMMAA) The caribou hunting site was part of a land bridge separating two lakes and connecting the tundra landscapes of Ontario and Michigan.

"It must have been really cold and really windy and pretty unpleasant," O'Shea said.

On the other hand, it was a corridor that caribou would have been forced to travel during their annual migration, making it an ideal hunting site.

Recognizing that, O'Shea consulted anthropologists who work with modern-day caribou hunters to find out what he should be looking for. He and his team then used sonar to map the bottom of the lake for signs of rock structures. Sure enough, they eventually found some small blinds that appeared to be used in fall hunts by individual families.

More recently, they discovered an elaborate community spring hunting setup, designed to trap animals coming from the opposite direction. It involves a 30-metre-long lane lined with short stone walls on either side that would have directed caribou into a natural cul-de-sac.

O'Shea said caribou and reindeer naturally follow lines on the ground – something that reindeer herders and caribou hunters still take advantage of today.

"It's not like the big bison kill where you stampede animals over cliffs," he said. "The lines just kind of pattern or shape their movement into the areas where the hunters want them to go."

The cul-de-sac was surrounded by simple stone hunting blinds consisting of a large rock and smaller ones on either side, forming a V-shape where a hunter could crouch, hidden, and then jump out from behind with a spear.

Unique preservation

Divers also sifted the sediment along the drive lanes and the cul-de-sac and in the hunting blinds and found stone flakes that would have been left behind during the crafting of spearheads and other tools.

While the fact that the site is now underwater made it difficult for archeologists to access, it also allowed the hunting structures to be preserved in a way they otherwise wouldn’t have, O'Shea said.

"If they had been on land, they would have been moved around by farming and highways and everything that goes on."

O'Shea said his team is now looking underwater for the caribou hunters' ancient campsites.

"If we can find campsites, we'll find a lot more information about the people themselves."