As far as I know, neutrino oscillation experiments have fairly conclusively demonstrated that neutrino states have mass. However, neutrinos are so frequently taken to be massless in cosmology that I began to wonder whether it would have made an appreciable difference in the early universe after the big bang if neutrinos were indeed massless.
Therefore, would the universe have turned out significantly differently if neutrinos were massless? If so, would that mean that there is some anthropic argument for neutrinos to be massive?