The world’s oldest meal has revealed that some of the earliest animals had physiological properties similar to humans and other present-day animals. Scientists from The Australian National University (ANU) have found new clues about the physiology of humans’ earliest animal ancestors that inhabited Earth more than 550 million years ago, by analysing the contents of the last meal consumed by them.
What is Ediacaran biota?
Ediacaran biota, which are the world’s oldest large animals, and were first discovered in the Ediacara Hills in South Australia’s Flinders Ranges, date back to 575 million years ago. Ediacaran biota, also known as Ediacaran fauna, is the unique assemblage of soft-bodied organisms preserved worldwide as fossil impressions in sandstone from the Ediacaran period, according to Britannica.
The Ediacaran period ranged from approximately 635 million to 541 million years ago. Ediacaran fauna represent an important development in the evolution of life on Earth, because they predate the explosion of life-forms at the beginning of the Cambrian Period 541 million years ago.
What did the world’s oldest animals eat?
The researchers from ANU found that the animals consumed bacteria and algae that were sourced from the ocean floor. The study describing the findings was recently published in the journal Current Biology. The findings unravel several mysteries about these strange creatures, including how they were able to consume and digest food.
What was found in the animals’ last meal?
According to the study, ancient fossils containing preserved phytosterol molecules remained from the animals’ last meal. Phytosterol molecules are a type of fat found in plants.
Kimberella and Ediacarans were unique creatures
The scientists analysed the molecular remains of what the animals ate, and confirmed that there was a slug-like organism, known as Kimberella, with a mouth and gut. It digested food the same way modern animals do.
Kimberella was probably one of the most advanced creatures of the Ediacarans, according to researchers.
The researchers found another animal. Known as Dickinsonia, the animal grew up to 1.4 metres in length and had a rib-like design imprinted on its body. It was less complex and had no eyes, mouth or gut.
Dickinsonia was an odd creature which absorbed food through its body as it traversed the ocean floor.
Kimberella had properties similar to humans
In a statement released by The Australian National University, Dr Ilya Bobrovskiy, the lead author on the paper, said the findings suggest that the animals of the Ediacaran biota, which lived on Earth prior to the Cambrian explosion of modern animal life, were a mixed bag of unusual creatures such as Dickinsonia, and more advanced animals like Kimberella that already had some physiological properties similar to humans and other present-day animals.
The Cambrian Explosion was a major event that forever changed the course of evolution of all life on Earth, and about 20 million years prior to this event, Kimberella and Dickinsonia lived on the planet. The two creatures have a structure and symmetry unlike anything that exists today.
Dr Bobrovskiy said Ediacaran biota are the oldest fossils large enough to be visible with one’s naked eyes, and are the origin of humans and all animals that exist today. He added that these creatures are humans’ deepest visible roots..
Why animals of the Ediacaran biota were large
Professor Jochen Brocks, a co-author on the paper, said algae are rich in energy and nutrients, and may have been instrumental for Kimberella’s growth.
Professor Brocks added that the energy-rich food may explain why the organisms of the Ediacaran biota were so large. He explained that nearly all fossils that came before the Ediacaran biota were single-celled and microscopic in size.
How the study was conducted
The ANU scientists used advanced chemical analysis techniques to extract and analyse the sterol molecules contained in the fossil tissue. Back in 2018, the ANU team was able to confirm that Ediacaran biota are among humans’ earliest known ancestors, by analysing cholesterol, which is the hallmark of animals.
The researchers could decipher what the animals ate in the lead up to their death using these sterol molecules, which contained tell-tale signatures. Differentiating between the signatures of the fat molecules of the creatures themselves, the algal and bacterial remains in their guts, and the decaying algal molecules from the ocean floor that were all entombed together in the fossils was the difficult part, Professor Brocks said.
He added Kimberella knew exactly which sterols were good for it and had an advanced fine-tuned gut to filter out the rest.
Professor Brocks also said that by using preserved chemicals in the fossils, they were able to make the gut contents of animals visible even if the guy had long since decayed. They used the same technique on weirder fossils like Dickinsonia to figure out how it was feeding and discovered that Dickinsonia did not have a gut.
In 2018, Dr Bobrovskiy retrieved both the Kimberella and Dickinsonia fossils from steep cliffs near the White Sea in Russia. This is a remote part of the world home to bears and mosquitoes.