Microscopic creatures discovered may be 'earliest remains' of human lineage.
Scientists have discovered a 'lost world' of ancient organisms in billions of years old rocks in northern Australia. According to the researchers, their findings could change the world's understanding of the earliest human ancestors.
Photo: James Cook University
The microscopic creatures known as the protosterol biota are part of a family of organisms called eukaryotes and lived in the Earth's waterways about 1.6 billion years ago, researchers say.
As Al Jazeera explains, eukaryotes have a complex the cellular structure that includes the mitochondria, the “energy center” the cell, and the nucleus, its «control and information center».
Modern forms of eukaryotes include fungi, plants, animals, and single-celled organisms such as amoeba.
Humans and all other germ-forming beings can trace their ancestry back to the Last Common Eukaryotic Ancestors (LECA) who lived more than 1.2 billion years ago.
New discoveries “seem to be the oldest remnants of our own lines — they lived before LECA”, says Benjamin Nettersheim, who did his PhD at the Australian National University (ANU) and is currently based at the University of Bremen in Germany.
“These ancient creatures were abundant in marine ecosystems around the world and likely formed ecosystems for much of Earth's history”, – continues the scientist.
The discovery of the protosterol biota is the result of 10 years of work by researchers at the Australian National University and was published in the journal Nature on Thursday.
Jochen Brox of ANU, who made the discovery with Nettersheim, said that the protosterol biota was more complex than bacteria, and presumably larger, although it is not known what they looked like.
«We believe they may have been the first predators on Earth to hunt and devour bacteria,» the professor said in a statement.
Researchers from Australia, France, Germany and the United States have examined the molecules of fossil fat, found inside rocks that formed on the ocean floor near what is now Australia's Northern Territory.
Northern Australia is known for containing some of the best-preserved sedimentary rocks dating back to the Earth's Middle Ages (mid-Proterozoic period), including the oldest biomarker-bearing rocks on Earth.
“Molecular fossils found in these ancient sediments provide unique insights into early life and ecology,» Nettersheim said.
The researchers found that the molecules had a primordial chemical structure that hinted at the existence of early complex creatures that evolved before LECA and since extinct.
“Without these molecules, we would never have known about the existence of the protosterol biota. The early oceans were mostly a bacterial world, but our new discovery shows that this probably wasn't the case,» Nettersheim said.
Brocks said these creatures probably flourished from about 1, 6 billion years ago to about 800 million years ago.
The end of this period on the Earth's evolutionary timeline is known as the Thonian Transformation, when more advanced organisms such as fungi and algae began to flourish. But it is not known exactly when the protosterol biota became extinct.
“The Thonian transformation is one of the deepest ecological turning points in the history of our planet, – says Brox. – Just as dinosaurs had to die out so that our mammalian ancestors could become large and abundant, perhaps the protosterol biota should have disappeared a billion years earlier to make way for modern eukaryotes”.