A new analysis of ancient chemical fossils has rocked the cradle of early animal evolution, bumping back compelling evidence of animal life to at least 635 million years ago.
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The findings, published in the Feb. 5 Nature, suggest that the ancient ancestor of fully formed animals survived a massive glaciation that enshrouded the Earth in ice at the end of the aptly named Cryogenian period. Debate continues over how much of the planet was frozen during two ice ages, each possibly a “snowball Earth” event that flanked this period, which extended from about 790 million to 630 million years ago.
The new results suggest that even if glaciers reached the equator during the second ice age, it is likely that warm pockets, perhaps created by volcanic activity or hydrothermal vents, may have persisted and harbored life.