On Aug. 10, Marshall County Conservation staff discovered what appeared to be a human jawbone while conducting a biological and wildlife survey in the Iowa River.
Deputies conducted a search of the area and identified three other potentially human bones.
The Marshall County Medical Examiner was contacted to collect the remains. The bones were eventually sent to the Iowa State Medical Examiner's Office for further testing.
The medical examiners confirmed the jawbone to be human, but said they held "with no modern medical significance." Experts believe the jawbone likely belonged to a prehistoric Native American.
The remaining bones were determined non-human.
The jawbone has been transferred to the Office of the State Archaeologist at the University of Iowa for further examination and research.