MARSHALL COUNTY, Iowa (WHO) — A bone found in a dry bed of the Iowa River earlier this summer is a human jawbone, authorities said, belonging to a prehistoric Native American.

The bone was found in early August by staff with the Marshall County Conversation Department. They found the bone and several others while conducting a wildlife survey. The bones were sent to the Office of the Iowa State Medical Examiner for testing.

The tests found one bone was a human jawbone, the others were not human remains.

The jawbone was sent to the Office of the State Archaeologist at the University of Iowa for further examination. Researchers there believe the bone is that of a prehistoric Native American.