sol = π / 4 from flavor physics - a new evidence for grand unification ?

We argue that there exists simple relation between the quark and lepton mixings which supports the idea of grand unification and probes the underlying robust bimaximal fermion mixing structure of still unknown flavor physics. In this framework the quark mixing matrix is a parameter matrix describing the deviation of neutrino mixing from exactly bi-maximal, predicting θsol+θC = π/4, where θC is the Cabibbo angle, θatm + θ CKM 23 = π/4 and θ 13 ∼ θ 13 ∼ O(λ), in a perfect agreement with experimental data. Both non-Abelian and Abelian flavor symmetries are needed for such a prediction to be realistic. An example flavor model capable to explain this flavor mixing pattern, and to induce the measured quark and lepton masses, is outlined.