558-Million-Year-Old Fat Molecules Confirm Earliest Known Animal On Record

A Dickinsonia fossil. The Australian National University (ANU)

It took a helicopter ride to the remote cliffs of the White Sea in Russia, clouds of mosquitoes, roaming bears, a rappel down 80-meter (260-foot) cliffs, and digging out blocks of sandstone, but researchers have found what they are calling a “Holy Grail” discovery.

A team of scientists from The Australian National University (ANU) and overseas have discovered molecules of fat in an ancient Dickinsonia fossil. The new finding places strong evidence on one side of a contentious, 75-year debate: What are Dickinsonia? One of the earliest animals on Earth? Large single-celled amoeba? Lichen? Something else entirely?


The finding, published in the journal Science, bestows the creature with the illustrious title of Earth’s earliest confirmed animal in the geological record.

“The fossil fat now confirms Dickinsonia as the oldest known animal fossil, solving a decades-old mystery that has been the Holy Grail of paleontology,” said Jochen Brocks, associate professor from the ANU Research School of Earth Sciences, in a statement.

Not only that but the “molecules that we’ve found prove that animals were large and abundant 558 million years ago, millions of years earlier than previously thought," he added.

The question of its identity has remained problematic for decades due to the natural degradation of organic matter and the creature’s unique morphological traits. 

Organic matter from Dickinsonia. The Australian National University (ANU)

“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 paleontologists studied for many decades,” explained ANU PhD scholar Ilya Bobrovskiy.

Due to such conditions, organic matter from Dickinsonia fossils has never been found before. Most of the creature's preservation has been in the form of imprints or traces, with their squishy, shell-less bodies breaking down over time. However, Bobrovskiy and his colleagues managed to unearth a fossil so well preserved that the team were able to extract cholesterol, a type of fat essential for animal life. 

While cholesterol breaks down over time, the products of its decay are specific and can be preserved. Using a newly developed method to test for fossil sterols, they found an abundance of cholesteroids (up to 93 percent) compared to the surrounding sediment (11 percent). The fossils also didn’t have ergosteroids, a known characteristic of fungi.

Ediacaran fossils, within which Dickinsonia are considered an iconic genus, are as “strange as life on another planet,” according to the authors. In general, these oval-shaped creatures could be as minuscule as a few millimeters to as big as a bathmat, with rib-like segments jutting from a central groove along its body. The creature lived about 20 million years before the Cambrian explosion, a period when complex, multicellular life began to emerge, diversify, and evolve at an incredibly rapid pace.


Although it's possible that Dickinsonia is a new form that creates cholesterols but is not an animal, it's unlikely. This new discovery suggests the “creature was in fact our earliest ancestor,” added Brocks.