A caribou hunting site, built by native people 9,000 years ago, has been discovered underneath Lake Huron. 

Stones laid in V-shaped formations and simple lanes mark the most extensive hunting architecture yet found beneath any of the Great Lakes. A pair of parallel lanes, each 98 feet long and 26 feet wide, leads to a dead end. Researchers believe these may have been used to corral caribou, while the V-shaped formations may have acted like hunting blinds, researchers said. The entire structure measures 330 feet by 92 feet. 

University of Michigan researchers discovered the ruins using a remotely operated vehicle (ROI) and sonar.  

Ninety centuries ago, the Alpena-Amberley Ridge, a temporary land bridge, allowed animals to walk from southern Ontario, down to northeast Michigan. This area is currently covered in 120 feet of water. 

"This feature, on older nautical charts labeled as Six Fathom Shoal, is an outcrop of limestone and dolomite which, during the period 9800 to 7000 years ago, formed a dry land corridor which divided the modern Lake Huron basin into two distinct lakes," John O' Shea of the University of Michigan wrote on his university webpage. 

Computer simulations of migrations in the ancient landscape suggest the animals would have converged, twice a year, at two "bottlenecks" during their journey. One of these locations was the area where the formations were found. 

Researchers believe the land bridge provided a natural hunting ground for the caribou, which were followed by human hunters. Animals were fattest in the fall, and investigators believe this was likely the season that provided the best hunting of the year. 

The archeological team believes that the native people at the time used two differing strategies to hunt the animals, depending on the time of year. In springtime, caribou instinctively followed the lanes into a dead end, where they were ambushed by a large group of hunters working together. In spring, smaller groups of natives used the smaller V-shaped blinds to hunt their prey head-on.

"This concentration of differing types of hunting structures associated with alternative seasons of migration is consistent with caribou herd movement simulation data indicating that the area was a convergence point along different migration routes, where the landform tended to compress the animals in both the spring and autumn," researchers wrote in a press release announcing the discovery. 

When divers examined the ruins, they found nine examples of chipped stone flakes, likely used to maintain tools. These provided further evidence the area was used to hunt the large mammals.  

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