A frozen world
850-635 million years ago
Earth froze over again, twice, in the space of 200 million years. The ice may well have stretched all the way from the poles to the equator. This second Snowball period may have triggered the evolution of the first complex animals. The first complex organisms, weird tube- and frond-shaped things called the Ediacarans, appeared soon after.
See other: History of Life
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