 This suggests strongly that these crop circles were more likely to be caused by intentional human action than by paranormal activity.Another strong indication of that theory was that inhabitants of the zone with the most circles had a historical tendency for making large-scale formations, including stone circles such as Stonehenge, burial mounds such as Silbury Hill, long barrows such as West Kennet Long Barrow, and .In 1991, self-professed pranksters Doug Bower and Dave Chorley made headlines claiming it was they who started the phenomenon in 1978 with the use of simple tools consisting of a plank of wood, rope, and a baseball cap fitted with a loop of wire to help them walk in a straight line.