A Review of the Neoproterozoic Global Glaciations and a Biotic Cause of Them

In the Neoproterozoic Era, the Earth experienced two broad intervals of global glaciation, commonly known as Snowball Earth. There was also a rapid diversification of life, with the evolution of most of the eukaryotic lineages. Here, salient evidence for the Neoproterozoic global glaciations, including the carbon isotope record, is reinterpreted, and an alternative explanation for the causes of glaciation is proposed. The proliferation of life could have led to increases in atmospheric O levels and concomitant decreases in CO and CH. Coupled biochemical and geochemical changes would have led to global cooling and glaciation. This so-called biotic hypothesis of the Snowball Earth is consistent with the most salient features of the reported evidence and explains the consecutive episodes of global glaciation.