 The dominant view since the 1960s has been that the increasing use of iron led to social changes in Britain.Deposits of iron ore were separated from the sources of tin and copper necessary to make bronze, and as a result trading patterns shifted and the old elites lost their economic and social status.Archaeologist Barry Cunliffe believes that population increase played a role and has stated "the forts provided defensive possibilities for the community at those times when the stress of an increasing population burst out into open warfare.