A neutrino mass-mixing scheme which explains qualitatively all present evidence for neutrino mass (the solar and atmospheric neutrino deficits, LSND, and significant hot dark matter) also successfully avoids the “alpha effect”, allowing r-process nucleosynthesis in the neutrino-heated ejecta of supernovae. The properties of neutrinos required to ensure production of heavy nuclei provides independent evidence for (1) at least one light sterile neutrino,&ngr;s;(2) a near maximally-mixed&ngr;&mgr;−&ngr;&tgr;doublet (which also explains the atmospheric anomaly and provides hot dark matter) split from a lower mass&ngr;e−&ngr;sdoublet (needed also for the solar&ngr;edeficit); (3)&ngr;&mgr;−&ngr;emixing≳10−4;and (4) a splitting between the doublets (measured by the&ngr;&mgr;−&ngr;emass difference) ≳1 eV2, favoring the upper part of the LSND range. There is a quantitative problem with the solar observations, which do not in detail fit this or any other model. If, however, the&ngr;sis a bulk neutrino in extra dimensions the nearness in mass of the zero mode to the&ngr;eprovides vacuum oscillations, while the Kaluza-Klein states give MSW oscillations, and all the solar data can be fit. ©2000 American Institute of Physics.