  We argue that the chiral anomaly of $\Ncal = 1$ super Yang-Mills theory
admits a dual description as spontaneous symmetry breaking in M theory on $G_2$
holonomy manifolds. We identify an angle of the $G_2$ background dual to the
anomalous $U(1)_R$ current in field theory. This angle is not an isometry of
the metric and we therefore develop a theory of ``massive isometry'' to
describe fluctuations about such angles. Another example of a massive isometry
occurs in the Atiyah-Hitchin metric.
