Correlation between "Snowball Earth" and Cambrian Explosion I know there is a theory that the earth was once covered in ice that precisely pre-dates the cambrian explosion. is there a leading idea of how snowball earth allowed for the blossoming of multicellular organisms? Did the ice sheets serve as a protective barrier for multicellular organism to evolve? I'm just curious if there are any prevailing theories on this matter. The cambrian explosion is a very mysterious era in evolution and wondering if the global ice sheet had something to do with it or whether snowball earth was just a coincidence.