Complex sentence: Despite not being joined to the mainland by bridge until 1908, axe and arrow heads that date from the bronze age have been found on Walney indicating that people have been living on the island for at least around 3,000 years.
Split into simpler sentences: Despite not being joined to the mainland by bridge until 1908, axe and arrow heads that date from the bronze age have been found on Walney. So people have been living on the island for at least somewhere around 3,000 years.