These tiny creatures were key to life forming on Earth

In an unlikely discovery, rocks from Maryland in the United States have helped us uncover the tiny creatures that triggered life on Earth.

That's right, prehistoric marine worms could have made a significant contribution to the Great Ordovician Biodiversifiaction Event.

"It's really incredible to think how such small animals, ones that don't even exist today, could alter the course of evolutionary history in such a profound way," said Johns Hopkins University geobiologist Maya Gomes.

Researchers found increased levels of a mineral known as pyrite in a specific sediment level across nine sites in Chesapeake Bay. A steady supply of oxygen is required for pyrite to form from sediment minerals, but it also easily reacts with oxygen.

But the more pyrite that forms and is then locked away under the ground, the most oxygen concentrations can build up.

"It's kind of like Goldilocks," explains Johns Hopkins paleoclimatologist Kalev Hantsoo. "The conditions have to be just right. You have to have a little bit of mixing to bring the oxygen into the sediment, but not so much that the oxygen destroys all the pyrite and there's no net buildup."

The levels of pyrite in the sediment suggests something was churning the ocean floor to keep this mineral from stealing back too much of the increasing oxygen levels.

Hantsoo and colleagues strong suspect these early sediment mixers were the worms burrowing away, along with other creatures interacting with the seafloor.

"We hypothesize that pyrite burial […] increased during the protracted onset of bioturbation," the researchers explain.

So it seems that these burst of oxygen, partially produced by the worms' excavations, helped life's diversity burst onto Earth.

"There's always been this question of how oxygen levels relate to the moments in history where evolutionary forces are ramped up and you see a greater diversity of life on the planet," says Gomes.

"With this work, we'll be able to examine the chemistry of early oceans and reinterpret parts of the geological record."

Worms continue to play a great role in bioturbation today, physically mixing up the top layers of soil, allowing fluid and oxygen enhance and cycling of other important nutrients, including iron, sulfur and carbon dioxide.

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