  As a minimal theory of fermion masses we extend the SM by heavy vectorlike
fermions, with flavor-anarchical Yukawa couplings, that mix with chiral
fermions such that small SM Yukawa couplings arise from small mixing angles.
This model can be regarded as an effective description of the fermionic sector
of a large class of existing flavor models and thus might serve as a useful
reference frame for a further understanding of flavor hierarchies in the SM.
Already such a minimal framework gives rise to FCNC effects through exchange of
massive SM bosons whose couplings to the light fermions get modified by the
mixing. We derive general formulae for these corrections and discuss the bounds
on the heavy fermion masses. Particularly stringent bounds, in a few TeV range,
come from the corrections to the Z couplings.
