Around 2.4 billion years ago, the Great Oxidation Event caused fundamental changes to the chemistry of Earth’s surface environments. However, the effect of these changes on the biosphere is unknown, due to a worldwide lack of well-preserved fossils from this time. In new research, paleontologists examined exceptionally preserved, large spherical microfossils permineralized in chert from the lower part of the 2.4-billion-year-old Turee Creek Group in Western Australia.
“The Great Oxidation Event is thought to have triggered a mass extinction and opened the door for the development of more complex life, but little direct evidence had existed in the fossil record before the discovery of the new microfossils,” said Professor Erica Barlow, a researcher at the University of New South Wales and the Pennsylvania State University.
“What we show is the first direct evidence linking the changing environment during the event with an increase in the complexity of life.”
“This is something that’s been hypothesized, but there’s just such little fossil record that we haven’t been able to test it.”
“When compared to modern organisms, the microfossils more closely resembled a type of algae than simpler prokaryotic life — organisms like bacteria, for example — that existed prior to the Great Oxidation Event.”
Algae, along with all other plants and animals, are eukaryotes, more complex life whose cells have a membrane-bound nucleus.
More work is required to determine if the Turee Creek Group microfossils were left behind by eukaryotic organisms, but the possibility would have significant implications. It would push back the known eukaryotic microfossil record by 750 million years.
“The microfossils have a remarkable similarity to a modern family called Volvocaceae,” Professor Barlow said.
“This hints at the fossil being possibly an early eukaryotic fossil. That’s a big claim, and something that needs more work, but it raises an exciting…
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