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That would be funny! It would mean they emerged right after the Huronian icehouse period ended, in the same way the Cambrian Explosion happened right after the Cryogenian period ended.

[] https://en.wikipedia.org/wiki/Greenhouse_and_icehouse_Earth

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IIRC this was associated to an early, brief spike in atmospheric oxygen. It went up, fell, and then took about one gigayear to increase again to large sustained levels closer to what we have today. Large organisms have low area to volume ratios, and require a high level of oxygen to scale up while producing enough energy. See https://ars.els-cdn.com/content/image/1-s2.0-S16749871120008...

Source: https://www.sciencedirect.com/science/article/pii/S167498711...

> while producing enough energy

“while transforming enough energy” is both more accurate but also educates the lay reader by hinting at the processes involved.

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