After closely examining the fossils of 555-million-year-old organisms, a team of scientists has discovered that Earth’s early ecosystems were vastly more complex than anyone has previously suspected.

Scientists from Canada, the United Kingdom, and the United States joined forces to craft a computer model that replicated the habitat of the Tribrachidium, a now extinct organism that once lived in the southern oceans.

The Tribrachidium lived 635 to 541 million years ago during a period of time known as the Ediacaran Era. During this time, the Earth was inhabited by a wide variety of large, complex organisms, however, few if any of them can be linked to modern species.

“Because we have no obvious modern comparison, that’s made it really hard to work out what this organism was like when it was alive — how it moved, if it moved, how it fed, how it reproduced,” said Imran Rahman, Research Fellow in University of Bristol’s School of Earth Sciences .

Conventional wisdom held that these creatures formed simple ecosystems with one another and their environments. They were thought to have only rudimentary feeding methods. Yet, this new study, published in the journal Science Advances, suggests otherwise.

“The computer simulations we ran allowed us to test competing theories for feeding in Tribrachidium. This approach has great potential for improving our understanding of many extinct organisms,” said Rahman.

Using computational fluid dynamics, the team was able to demonstrate that the Tribrachidium most likely survived by feeding on particles floating in the water. This ‘suspension feeding’, as it is called, is fairly common in aquatic organisms today but was not known to have occurred so long ago.

“For many years, scientists have assumed that Earth’s oldest complex organisms, which lived over half a billion years ago, fed in only one or two different ways. Our study has shown this to be untrue, Tribrachidium and perhaps other species were capable of suspension feeding,” said Simon Darroch, Assistant Professor at Vanderbilt University.

As the Tribrachidium cannot move independently, it had to rely on ocean currents washing particles across its many crevices in order to absorb nutrients. This innovative solution suggests a hitherto unsuspected level of evolution.

Suspension feeding is a method that involves mobilizing ” organic material that was being carried around in the water column,” said Rahman. “It can increase passage of sunlight through water and potentially increase oxygenation, as well.”
“This demonstrates that, contrary to our expectations, some of the first ecosystems were actually quite complex.”