Revealed today, the fossil is a relic of a crucial turning point in the history of life: the appearance of the first living beings with more than one cell
The Earth is 4.5 billion years old, but a large number of these, with 9 zeros, does not say much if we can not imagine it. To overcome this barrier, let us advance slowly, using an analogy. There are 4.5 billion seconds, Dom Pedro II was the Emperor of Brazil, and slavery would still take 14 years to be abolished. It was in 1874.
If Earth were 4.5 billion seconds old (that is, if she had been born in 1874), she would be 144 years old. The human species, with its humble 300,000 years, would have existed for three and a half days. Nothing, essentially.
To be fair, it is not just Homo sapiens that has lasted a wink: animals as a whole have emerged very recently. Until Earth’s 127th birthday (note that it was already extremely old by this time), all living things were still unicellular and microscopic.
Sometimes they formed fairly cooperative colonies, but they stopped there. The game only turned into the Cambrian explosion 541 million years ago – a mere seventeen years ago, on our convenient, seconds-based scale.
The Cambrian explosion is the name given by geologists to the time when large, complex animals suddenly appear in the fossil record. It was a fast-paced chapter in natural history, where large, tricky life forms – such as slugs, snails, and insects – popped up after billions of years of microscopic boredom and unenthusiastic sex between bacteria.
If the Cambrian explosion was as legendary as the Rolling Stones’ presentation at Copacabana in 2006, the oval bug in the photo above would be tantamount to the opening show of the Titans. It was a preview, an appetizer of what multicellular life would become.
Dickinsonia, as it was christened, is the oldest animal fossil ever found: it lived 558 million years ago, 17 million years before zero.
It was found by Russian doctoral student Ilya Bobrovskiy on a steep slope on the shores of the White Sea – the name for the portion of absurdly frozen water that separates northern Finland from Russia.
The analysis of small fragments of organic matter present both in the fossil itself and in the rock around it (fragments of which the preservation is rare) have made it possible to establish without a shadow of a doubt that the saying of which was an animal and not some other form of pre-life -historical. The analysis was published today.
Dickinsonia is part of a group of pre-Cambrian multicellular organisms (that is, prior to the Cambrian explosion) called “biota ediacarana”. These little faces were a mystery to science, for although their fossils have always indicated that they were more than mere colonies of bacteria, they could not know what exactly they were.
They were in a limbo of sorting. Bobrovskiy’s discovery solved this dilemma: we now know, beyond a shadow of a doubt, that the Ediacaranans were animals. Animals before animals; the oldest known animals.
Such organic fragments mentioned above are somewhat banal: cholesterol. Cholesterol with a chemical composition such that it can only be found in animals. A thinner Edgar might have not been able to tell this story.
“This is exactly the kind of fat that delivered Dickinsonia was actually an animal,” Jochen Brocks of the National University of Australia, one of those who worked on the analysis, told The Guardian. A toast to overweight Ediacaran.