First Animal: Before Cambrian Explosion, Sea Sponges Probably Lived First on Earth, Says Study

The animal that beat us all to the Earthly starting mark was likely a sea sponge.

That is, first animal on the planet? That one, say MIT researchers who conducted genetic analyses in a recent study, concluding that a strange molecule present in certain rocks 640 million years old came from sea sponges.

Those are rocks from before the Cambrian explosion -- when most animal groups populated the planet, 540 million years before now. Knowing that most groups weren't around then, this suggests that the sponges may have been Earth's first animal inhabitants.

"We brought together paleontological and genetic evidence to make a pretty strong case that this really is a molecular fossil of sponges," David Gold, a postdoc at MIT, said in a release. "This is some of the oldest evidence for animal life."

Outside of a bathtub and in their live form in a marine environment, sponges are multi-cellular animals. One latches onto something solid in a place where the hope is that food will come by. Sponges' scientific name, Porifera, means "pore-bearing" -- the pores on the outside of one lead to canals and to the creature's interior. These simple animals are filter feeders that capture and consume particles as tiny as bacteria and in larger pieces as well.

The study findings were recently published in the journal Proceedings of the National Academy of Sciences.

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