Complex sentence: On March 26,2011, hikers discovered a partial human skull later determined to be that of Mike Riemer in an area within a mile radius of where Robertson's body had been discovered in 1986.
Split into simpler sentences: On March 26,2011, hikers discovered a partial human skull later determined to be that of Mike Riemer. It was found in an area within a mile radius of where Robertson's body had been discovered in 1986.