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Two teams of scientists have resolved a longstanding controversy over the origins of complex life on Earth.
The joint studies found that molecular fossils extracted from 635-million-year-old rocks are not the earliest evidence of animals, but instead common algae.
Researchers from the Australian National University (ANU), Max Planck Institute and Caltech say the discovery has big implications for our understanding of evolution.
“It brings the oldest animal evidence of nearly 100 million years closer to the present day,” said Dr. Lennart van Maldegem of the ANU, co-author of a study.
“We were able to show that some common algae molecules can be altered by geological processes, leading to molecules indistinguishable from those produced by sponge-like animals.
Professor Jochen Brocks, also an ANU resident, said the mystery of when our very first animal ancestors emerged and became abundant in the oceans has puzzled paleontologists for more than a century.
‘Ten years ago, scientists discovered molecular fossils of an animal steroid in rocks that once lay at the bottom of an ancient Middle Eastern sea,’ said Professor Brocks.
“The big question was: how could these sponges have been so abundant, covering much of the seafloor around the world, but leaving no body fossils?”
Dr Ilya Bobrovskiy, lead author of the other study, said the researchers were able to “solve this mystery.”
“While he claims that true sponges are the only living organism capable of producing these steroids, the chemical processes can mimic biology and transform common and abundant algae sterols into ‘animal’ sterols,” he said.
‘These molecules can be generated in the laboratory when simulating geological weather and temperatures, but we have also shown that such processes occurred in ancient rocks.’
The two complementary studies were published in Nature, ecology and evolution.
AUSTRALIAN NATIONAL UNIVERSITY
Header Image Credit: Ilya Bobrovskiy
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