Cryogenian (635-850 Ma) sedimentary successions from Svalbard preserve transitions between glacial "Snowball Earth" and interglacial episodes during an important interval in the diversification of early eukaryotes. Our work, including field observations, UAV photography, clumped-isotope thermometry, synchrotron-based characterizations of Mn and Fe oxidation states, and identification of biomarkers allow us to reconstruct the environments that inhibited and prohibited the evolution of early animals.