By Elton Gomes
A new study has revealed that a fossilised lifeform, which existed 558 million years ago, has been identified as the oldest known animal.
Fat molecules have been discovered on the fossil of a mysterious creature called Dickinsonia. This discovery has confirmed that the creature lived 558 million years ago, thus making it the earliest known member of the animal kingdom. As per the findings, Dickinsonia has been known to exist 20 million years before the Cambrian Explosion, which was an event where major animals began appearing on the fossil record.
The Dickinsonia fossil was first discovered by Australian scientists around the year 1947. The recent study, which was published in the journal Science, ends a decades-long debate to identify what exactly was the Dickinsonia fossil.
What does the research say?
The study said that scientists have discovered molecules of fat in an ancient fossil of an oval shaped creature called Dickinsonia, which can grow up to 1.4 metres in length. This animal with rib-like segments running along its body belonged to the Ediacara Biota that lived on Earth 20 million years before the Cambrian explosion could take place.
The team discovered the fossil to be so well preserved in a remote area near the White Sea in the northwest of Russia that the tissue still contained molecules of cholesterol a type of fat that is the indicator of animal life. The presence of fat on the fossil confirmed Dickinsonia to be the oldest known animal fossil, researchers said.
It is the exact type and composition of that fat that was the giveaway that Dickinsonia was in fact an animal, said Jochen Brocks from the Australian National University (ANU), one of the authors of the study. Brocks added that the study solves a decades-old mystery that has been the holy grail of palaeontology, the Guardian reported.
The fossil fat molecules that we’ve found prove that animals were large and abundant 558 million years ago, millions of years earlier than previously thought, Brocks added, CNN reported.
Brocks further said, “Scientists have been fighting for more than 75 years over what Dickinsonia and other bizarre fossils of the Ediacaran Biota were: giant single-celled amoeba, lichen, failed experiments of evolution or the earliest animals on Earth. The fossil fat now confirms Dickinsonia as the oldest known animal fossil,” according to the CNN report.
Dickinsonia fossils have a worm-like resemblance
Dickinsonia fossils were first discovered in South Australia around the year 1947. The types of rocks they are found in and their lack of preserved skeletons suggest they could be soft-bodied marine creatures. However, little is known about which modern animals they are most closely related to. They look worm-like, but this may be a superficial resemblance, Brocks said, New Scientist reported.
Similar to todays animals, Brocks says that Dickinsonia might have used cholesterol to build cell walls. He added that other organisms tend to use different types of fat molecules.
Emily Mitchell, from the University of Cambridge, said that the cholesterol discovery is the best evidence that Dickinsonia was an animal. Mitchell, however, said that it could be possible that other species may have preceded it in the animal line. We might end up finding even older animal fossils, she said, as per the New Scientist report.
Other animals that could be older than Dickinsonia
Although scientists are unable to say exactly when the first animal arose, ancient traces indicate that it was more than 600 million years ago. However, Dickinsonia, with its newly confirmed classification, can be included among a group of the oldest animals found. Kimberella, an early mollusk-like animal, is older than the Dickinsonia in age. Helminthoidichnites were worm-like creature that likely left winding tracks, and are also known to be older than Dickinsonia.
Elton Gomes is a staff writer at Qrius