Fossils capture a turning point in the evolution of life

A team of researchers led by Curtin University has achieved a significant milestone in understanding the evolution of life on Earth. For the first time, the team has precisely dated some of the world’s oldest fossils of complex multicellular life. 

The study sheds light on a crucial point in Earth’s history when diverse life forms emerged in the oceans after four billion years of hosting only single-celled microbes.

The Ediacaran period

“The Ediacaran period represents a pivotal time in the evolution of life as it contains the earliest unequivocal fossil evidence for large-scale multicellular organisms, including the first animals,” wrote the study authors. 

“The Ediacaran biota demonstrates examples of heterotrophy, locomotion, sexual reproduction and organization into complex ecosystems.”

Dating the fossils 

Study lead author Anthony Clarke, a PhD student in the Timescales of Mineral Systems Group at Curtin, explained the innovative method used to determine the age of the ancient fossils. By utilizing volcanic ash layers as chronological markers within the geological sequence, the team was able to date the fossils with remarkable precision.

“Located in the Coed Cochion Quarry in Wales, which contains the richest occurrence of shallow marine life in Britain, we used outfall from an ancient volcano that blanketed the animals as a time marker to accurately date the fossils to 565 million years, accurate down to 0.1 percent,” said Clarke.

Ancient living community 

“With similar Ediacaran fossils found at sites around the world including in Australia, dating the fossils identifies them as being part of an ancient living community that developed as Earth thawed out from a global ice age.”

“These creatures would in some ways resemble modern day marine species such as jellyfish, yet in other ways be bizarre and unfamiliar. Some appear fern-like, others like cabbages, whereas others resembled sea pens.”

New geological period 

Study co-author Professor Chris Kirkland said the fossils are named after the Ediacara Hills in South Australia’s Flinders Ranges, where they were first discovered, leading to the first new geological period established in over a century.

“These Welsh fossils appear directly comparable to the famous fossils of Ediacara in South Australia,” said Professor Kirkland. “The fossils, including creatures like the disc-shaped Aspidella terranovica, showcase some of the earliest evidence of large-scale multicellular organisms, marking a transformative moment in Earth’s biological history.”

“Ediacaran fossils record the response of life to the thaw out from a global glaciation, which shows the deep connection between geological processes and biology.”

“Our study underscores the importance of understanding these ancient ecosystems in order to unravel the mysteries of Earth’s past and shape our comprehension of life’s evolution.”

The study is published in the Journal of the Geological Society.

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