Paleontologists have detected abundant protosteroids — traces of ancient life forms — in 1.6-billion-year-old sedimentary rocks that had formed at the bottom of the ocean near what is now Australia’s Northern Territory.
“All living eukaryotes evolved from the Last Eukaryotic Common Ancestor (LECA) that lived between around 1.2 billion and more than 1.8 billion years ago,” said University of Bremen paleontologist Benjamin Nettersheim and colleagues.
“LECA and all its descendants form the crown of the eukaryotic tree including algae, plants, fungi, animals and all extant, unicellular protists.”
“Yet, the domain Eukarya has a much deeper prehistory. The ancestral line leading towards LECA, and all its extinct side-branches, are stem-group Eukarya.”
“The genome and cell structure of living descendants provide only limited insights into the evolution of LECA’s ancestors, and almost nothing is known about their abundance, ecology and habitats.”
“To study the hundreds of millions of years of hidden eukaryote evolution and ecology, we have to search for fossil and chemical remains directly in the geological record.”
In their research, the scientists detected chemical traces of the so-called Protosterol Biota in 1.6-billion-year-old rocks of the Barney Creek Formation in northern Australia.
“These ancient creatures were abundant in marine ecosystems across the world and probably shaped ecosystems for much of Earth’s history,” Dr. Nettersheim said.
“The Protosterol Biota were certainly more complex than bacteria and presumably larger, although it’s unknown what they looked like,” added Australian National University’s Professor Jochen Brocks.
“We believe they may have been the first predators on Earth, hunting and devouring bacteria.”
According to the team, these creatures thrived from about 1.6 billion years ago up until about 800 million years ago.
The end of this period in Earth’s evolutionary timeline is known as the…
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