Sea cucumbers are among the earliest multicellular life forms on earth.

Sea cucumbers like the one above are among the oldest life forms still living on earth. Photo: Shutterstock

The largest mass extinction in Earth’s history happened 540 million years ago, and is known as the end-Ediacaran extinction. New fossil evidence from Namibia has helped to shine some light on what caused that extinction: animals.

Single-celled organisms dominated the planet until about 600 million years ago until the first multicellular organisms, known as Ediacarans, began to develop. These creatures were sedentary, rather like plants, but they eventually gave rise to the first animals, known as metazoans. These were creatures that could move around and subsisted either on other creatures, or things produced by those creatures, like animals today.

Once animals came along, they flourished, and there was a rapid development of diverse creatures, establishing most of the modern animal families: vertebrates, mollusks, arthropods, annelids, sponges, and jellyfish.

“These new species were ‘ecological engineers’ who changed the environment in ways that made it more and more difficult for the Ediacarans to survive, said Simon Darroch, a Vanderbilt University assistant professor who directed the study.

These creatures essentially wrought havoc on the existing Ediacarans, putting so much stress on those life forms that they drove them to extinction. The greatest extinction event in Earth’s history was not caused by geology, or a meteor impact, but was caused by changing ecosystems brought about by newly evolved organisms.

“There is a powerful analogy between the Earth’s first mass extinction and what is happening today,” Darroch said. “The end-Ediacaran extinction shows that the evolution of new behaviors can fundamentally change the entire planet, and today we humans are the most powerful ‘ecosystems engineers’ ever known.”

We have been changing ecosystems to serve our will for millennia, and we are only now realizing the extent to which those actions are impacting the world around us.

Ideally, we’ll be able to take this knowledge and figure out ways to preserve or even reestablish damaged ecosystems in order to prevent another, possibly far worse, extinction event.