John O’Shea on a prehistoric wooden object from the bottom of Lake Huron.

Under the cold clear waters of Lake Huron, University of Michigan researchers have found a five-and-a-half foot-long, pole-shaped piece of wood that is 8,900 years old. The wood, which is tapered and beveled on one side in a way that looks deliberate, may provide important clues to a mysterious period in North American prehistory.