World's oldest known fossils, now date back to 650 million years ago
The prior oldest known hard-bodied animals were reef-dwelling organisms
called Namacalathus, which date to approximately 550 million years
ago. Disputed remains for other possible soft-bodied animals date to between
577 and 542 million years ago.
The even more advanced age of the newly found sponge fossils provides
direct evidence that animal life existed before the severe "Snowball Earth"
event. The episode marked the end of Cryogenian Period 635 million years ago
and left much of the globe covered in ice. Early sponges somehow managed to survive, perhaps in watery refuges
around volcanic islands.
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