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Good point! I did include snowball Earth as one of the events in an earlier draft, but felt it was out of place and confusingly too similar to the writeup about Pannotia’s effects on life. There are many more theories on what contributed to the development of complex multicellular life, and it’s possible that it’s a result of multiple coinciding factors. But for this narrative centered on plate tectonics, I thought it made the story clearer to not include the snowball Earth hypothesis. This was the original writeup for the glaciation event: # Snowball Earth Between 715 to 635 million years ago, the Earth experienced a series of intense and extensive glaciations that covered the planet in ice. The earliest fossils of large multicellular life are dated soon after the end of these “Snowball Earth” conditions. Some theorise that the increased selective pressure during glaciation, followed by the return of vast coastal environments without competitors, helped drive the diversification of multicellular life. References Gee, H. (2021). A (Very) Short History of Life On Earth: 4.6 Billion Years in 12 Chapters. St. Martin's Publishing Group. McCall, G.J.H. (2006). The Vendian (Ediacaran) in the geological record: Enigmas in geology's prelude to the Cambrian explosion. Earth-Science Reviews, 77(1–3), 1-229. https://doi.org/10.1016/j.earscirev.2005.08.004. Lenton, T.M., Boyle, R.A., Poulton, S.W., Shields-Zhou, G.A., & Butterfield, N.J. (2014). Co-evolution of eukaryotes and ocean oxygenation in the Neoproterozoic era. Nature Geoscience, 7(4), 257–265. https://doi.org/10.1038/ngeo2108 |