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 located in different places to the tin and copper ore necessary to make bronze, and as a result trading patterns shifted and the old elites lost their economic and social status. Power passed into the hands of a new group of people.[10] Archaeologist Barry Cunliffe believes that population increase still 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.