Did environmental change cause multicellularity? Answer, we don't know.-We don't know but we do have evidence it can happen-http://discover.umn.edu/news/science-technology/university-minnesota-biologists-replicate-key-evolutionary-step-As an agnostic I don't claim to know very much if anything.-But going around saying we don't know is sort of pointless for me. -Give me data, and if you don't have data, evidence will do.