  We revisit four generations within the context of supersymmetry. We compute
the perturbativity limits for the fourth generation Yukawa couplings and show
that if the masses of the fourth generation lie within reasonable limits of
their present experimental lower bounds, it is possible to have perturbativity
only up to scales around 1000 TeV, i.e. the current experimental bounds and
perturbative unification are mutually exclusive. Such low scales are ideally
suited to incorporate gauge mediated supersymmetry breaking, where the
mediation scale can be as low as 10-20 TeV. The minimal messenger model,
however, is highly constrained. Lack of electroweak symmetry breaking rules out
a large part of the parameter space, and in the remaining part, the fourth
generation stau is tachyonic.
