"The fossil fat now confirms Dickinsonia as the oldest known animal fossil, solving a decades-old mystery that has been the Holy Grail of palaeontology".
The research has been published in the journal Science. But there was life - we have fossil evidence of a mysterious group of lifeforms known collectively as the Ediacaran biota. But the recent discovery of cholesterol in a Dickinsonia fossil determined that the creature is most definitely an animal.
The creature, known as Dickinsonia (yes, really), is believed to have been alive around 558 million years ago and could be found bimbling around on the bottom of the sea during the Ediacaran era. But Ilya Bobrovskiy, a PhD student at Australian National University, had to travel to a cold, remote area near the White Sea to find ones that still had preserved fat. It lived about 558 million years ago during the Ediacaran period, about 20 million years before the "Cambrian explosion", a period lasting tens of millions of years that has often been considered to mark the emergence of complex animals. Bobrovskiy et al. found a striking abundance of cholesteroids (up to 93%) in Dickinsonia fossils when compared to that in surrounding microbial mat-based sediment (approximately 11%).
The discovery of the fat confirms that the creature, dubbed "Dickinsonia", is the Earth's earliest known animal, according to the paper.
Mr Bobrovskiy said the team developed a new approach to study Dickinsonia fossils, which hold the key between the old world dominated by bacteria and the world of large animals that emerged 540 million years ago during the "Cambrian explosion".
The problem that was holding researchers back for so long was that Dickinsonia and other Ediacarans have boneless bodies that weren't easily preserved.
"Most rocks containing these fossils such as those from the Ediacara Hills in Australia have endured a lot of heat, a lot of pressure, and then they were weathered after that - these are the rocks that palaeontologists studied for many decades, which explained why they were stuck on the question of Dickinsonia's true identity", he added.
The fossils are impressions in rock: oval shapes with internal lines, looking somewhat like a leaf imprint densely packed with veins.
However, some Dickinsonia fossils in Russian Federation had retained organic matter. "I had to hang over the edge of a cliff on ropes and dig out huge blocks of sandstone, throw them down, wash the sandstone and repeat this process until I found the fossils I was after", said Ilya Bobrovskiy, an Australian researcher who discovered the fossil.
'These fossils were located in the middle of cliffs of the White Sea that are 60 to 100 metres high. Molecules of cholesterol, produced only by animals, were found inside the sample using advanced scanning techniques.
ANU researcher Ilya Bobrovskiy searches for fossils in the Zimnie Gory locality, Russia.
Brocks said being able to study molecules from these ancient organisms was a game-changer. But I also immediately saw the significance'. "But applying biomarkers removes a large part of this uncertainty".