Fossil traces found in an oil field on the Arabian Peninsula are the oldest evidence yet of animals, pushing back the known origins of higher life to more than 635 million years ago.
The animals' remains don't look like traditional fossils. They're more like fossil echoes: chemical traces of a compound only produced — at least in modern times — by demosponges, descendants of what some scientists consider to be the last common ancestor of all animals.
[via: http://blog.wired.com]
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Earliest Animals Were Sea Sponges, Fossils Hint
