 Examination of peat cores and pollen records indicates that soil erosion ( suggesting clearance of woodland for agricultural purposes ) was taking place in 3470 BC and that evidence of arable cultivation by Neolithic communities exists from <unk> BC . As the climate became damper , peat expanded at the expense of woodland , and post @-@ glacial sea level changes left raised beaches around the coastline 18 – 45 metres above the present coastline , especially between Harris and A <unk> . There are prehistoric fort sites at Kilmory , Papadil and Shellesder of uncertain date . 
