Might Second Oxygenation period ~600-700 million (?) years ago, be related to emergence of Animalia? The first Great Oxygenation Event was 2-2.5 Byrs ago; yet based iron formation goes back to even 3.5 Byrs ago. Second oxygenation, during the later Proterozoic, would seemingly be related to sources or sinks. For the latter, one might have had decreased gaseous output from volcanoes, traps, or marine hydrothermal vents; hence just a residual increase in ambient oxygen? Or perhaps mainly an increase in biomass and thus more photosynthesis accounting for such oxygenation. Would the latter increased biomass seem conducive to expansion firstly of herbivores etc. i.e. expansion of Animalia? Hence Second Oxygenation period, for latter part of Proterozoic, might have indirectly contributed to emergence of Animalia.
Another avenue of approach to the conundrum of Animalia emergence might be related to Cambrium ‘explosion’, wherein all phyla (plus extra now extinct phyla?) were already laid down. How long a period of evolution lead time would be required to be consistent with such result? Would 100 million years, at ~650 Myrs ago suffice? Is pre-Cambrium Ediacaran more likely to be a plant or animal fossil? Sponge animals extend back to ~600-700+ Myrs? Which would be more prevalent; and which would be more likely to be preserved? also see more elaborate Oct 26, 2014 blog.
http://www.nature.com Timothy W. Lyons, Christopher T. Reinhard, Noah J. Planavsky, The Rise of Oxygen in the Earth’s early ocean and atmosphere, Nature Vol 506, Feb. 20, 2014.
Lei Chen, Shuhai Xiao, Ke Pang, Chuanming Zhou, Xunlai Yuan, Cell Differentiation and germ-soma separation in Edicaran animal embryo-like fossils, Nature vol 516, Dec. 11, 2014, and references therein.