> We don't really have much ideas about why the CE happened Look at the graph here: http://en.wikipedia.org/wiki/Oxygen_catastrophe http://en.wikipedia.org/wi

> We don't really have much ideas about why the CE happened Look at the graph here: http://en.wikipedia.org/wiki/Oxygen_catastrophe http://en.wikipedia.org/wiki/Oxygen_catastrophe It took 1 Ga from the invention of photosynthesis to grow enough biomass so that photosynthesis started to be a notable process in geological scale. Then it took 0.5 Ga of photosynthesis, when the produced oxygen would dissolve into the oceans, until the oceans were saturated. Atmospheric oxygen remained at 2–4%. Then it tool 1.5 Ga of hard work, when the land surface minerals would be oxidized, until they were all oxidized and finally oxygen started to accumulate in the atmosphere. Then around 600 Ma ago the atmosphere hit above 10% oxygen, and this pretty much coincides with the Cambrian evolutionary explosion.