Illustration of animals that existed during the Ediacaran period (around 635 to 542 million years ... [+]
A study has used virtual recreations of the earliest known animal ecosystem to show how organisms changed the environment and boosted their evolution.
During the Ediacaran period (around 635 to 542 million years ago) fossils found first in the Ediacara Hills, Australia, testify the emergence of the first multicellular life. They include many weird creatures of unknown affinity, like Dickinsonia, a sort of hybrid between a worm and a jellyfish, Charnia, a segmented and branched organism, or Tribrachidium, showing a threefold rotational symmetry not found in any modern animal. But all were bottom-dwelling marine life forms attached to the sea bottom by root-like organs or resting on the sediment surface.
Using state-of-the-art computer simulations, the authors of a new study discovered how these animals mixed the surrounding seawater. This may have affected the distribution of important resources such as food particles and could have increased local oxygen levels, both changing the surrounding environment as boosting the evolution of more complex animals.
"It's exciting to learn that the very first animals from 580 million years ago had a significant impact on their environment, despite not being able to move or swim. We've found they mixed up the water and enabled resources to spread more widely—potentially encouraging more evolution," explains study coauthor Emily Mitchell from the University of Cambridge's Department of Zoology.
Scientists know from modern marine environments that nutrients like food and oxygen are carried in seawater, and that animals can affect water flow in ways that influence the distribution of these resources.
To test how far back this process goes in Earth's history, the team looked at some of the earliest examples of marine animal communities, known from rocks at Mistaken Point, Newfoundland, Canada. This world-famous fossil site perfectly preserves early life forms thanks to a cover of volcanic ash.
Owing to the exceptional preservation of the fossils, the scientists could recreate digital models of key species, which were used as a basis for further computational analyses.
"We used ecological modeling and computer simulations to investigate how 3D virtual assemblages of Ediacaran life forms affected water flow. Our results showed that these communities were capable of ecological functions similar to those seen in present-day marine ecosystems," so first author Susana Gutarra, a Scientific Associate at the London Natural History Museum.
The study showed that one of the most important Ediacaran organisms for disrupting the flow of water was the cabbage-shaped animal Bradgatia. The Bradgatia from Mistaken Point are among some of the largest fossils known from this site, reaching diameters of over 50 centimeters (or 20 inches).
This simulation shows how the organisms of the Ediacaran community caused turbulence and slowing ... [+]
By changing currents and causing turbulence, the scientists believe these Ediacaran organisms might have been capable of enhancing local oxygen concentrations and nourishment availability. This biological mixing might also have had repercussions for the wider environment, possibly making other areas of the sea floor more habitable and perhaps even driving evolutionary innovation by allowing more complex feeding behaviors—like branched tentacles to filter the currents—to evolve.
The Ediacara fauna went extinct about 539 to 500 million years ago, marking the end of the Proterozoic Eon and the beginning of the Phanerozoic Eon - the time in earth's history ruled by modern animal groups.
Imran Rahman, lead author and Principal Researcher at the Natural History Museum, concludes that: “The approach we’ve developed to study Ediacaran fossil communities is entirely new in paleontology, providing us with a powerful tool for studying how past and present marine ecosystems might shape and influence their environment.”
The full research paper "Ediacaran marine animal forests and the ventilation of the oceans" was published in the journal Current Biology and can be found online here.
Additional material and interviews provided by the University of Cambridge.
