  In the Standard Model, Yukawa couplings parametrize the fermion masses and
mixing angles with the exception of neutrino masses. The hierarchies and
apparent regularities among the quark and lepton masses are, however, otherwise
a mystery. We propose a new class of models having vector-like fermions that
can potentially address this problem and provide a new mechanism for fermion
mass generation. The masses of the third and second generations of quarks and
leptons arise at tree level via the seesaw mechanism from new physics at
moderately higher scales, while loop corrections produce the masses for the
first generation. This mechanism has a number of interesting and testable
consequences. Among them are unavoidable flavor-violating signals at the
upcoming experiments and the fact that neutrinos have naturally only Dirac
masses.
