New Theory Into What Caused a Mass Extinction Event in Earth's History

There have been five mass extinction events in Earth's 4.5-billion-year history that were driven by environmental factors, scientists say. But one that's considered the first mass extinction of more complex life was not likely caused by a meteorite impact or volcanic eruptions as scientists have theorized for others.

An Ediacaran fossil form south Australia. (Image source: James St. John via Flickr)

New research from Vanderbilt University suggests that the mass extinction, which occurred 540 million years ago, might have been initiated by the life on Earth itself.

“People have been slow to recognize that biological organisms can also drive mass extinction,” Simon Darroch, assistant professor of earth and environmental sciences at Vanderbilt University, said, according to the university's research news. “But our comparative study of several communities of Ediacarans, the world’s first multicellular organisms, strongly supports the hypothesis that it was the appearance of complex animals capable of altering their environments, which we define as ‘ecosystem engineers,’ that resulted in the Ediacaran’s disappearance.”

The study published in the journal Proceedings of the Royal Society B described how researchers' analysis Ediacaran fossils at a specific site and strata in Namibia called the Farm Swartpunt revealed that there was "significantly lower genus richness than older assemblages."

The study authors also conducted analysis on the geochemical composition and sediment of samples and found that environmental stressors were probably not factors that accounted for lower numbers. So, what did?

Around the time these soft-bodied organisms began to disappear was also the start of what's known as the Cambrian explosion, a time period characterized by a relative burst in animal diversity, specifically those with shells and skeletons.

“These new species were ‘ecological engineers’ who changed the environment in ways that made it more and more difficult for the Ediacarans to survive,” Darroch explained, according to the university.

Darroch told New Scientist that the newer species of the Cambrian explosion might have eaten the Ediacarans, explaining that they saw a fossil of a predatory sea anemone near an Ediacaran.