Where does flavour mixing come from?

We argue that flavour mixing, both in the quark and charged lepton sector, is basically determined by the lightest family mass generation mechanism. S o, in the chiral symmetry limit when the up and down quark masses vanish, a ll the quark mixing angles vanish. This mechanism is not dependent on the: number of quark-lepton families nor on any "vertical" symmetry structure, u nifying quarks and leptons inside a family as in Grand Unified Theories. To gether with a hypothesis of maximal CP violation, the model leads to a comp letely predictive ansatz for all the CKM matrix elements in terms of the qu ark masses. Some implications for neutrino masses and oscillations are brie fly discussed, (C) 1999 Published by Elsevier Science B.V. All rights reser ved.