Fungi are so much more than a topping on your pizza. While this unassuming kingdom of organisms might not get the same love or respect as plants or animals, they play an unbelievably crucial role in the story of life on planet Earth.
That’s why scientists are so excited to announce the discovery of the world’s oldest fungi fossils. The minuscule fossils date to somewhere between 900 million and 1 billion years ago, pushing back the previously confirmed record holder for the world’s first fungus fossil by almost half a billion years.
At the grand old age of 1 billion, it looks like this discovery could also be a candidate for some of the earliest multicellular life on land.
“Fungi are one of the more diverse groups of eukaryotes known today and, despite this, their ancient fossil record is very scarce,” study author Corentin Loron from the University of Liège in Belgium told IFLScience.
Reported in the journal Nature, the Ourasphaira giraldae microfossils were found in the shale of the Arctic coast in the Northwest Territories of Canada. Using an electron microscope, Loron and his team were able to denote tiny structures – double-layered cell walls, branching filaments, and spore-like spheres – that strongly suggested these were indeed fungi. The cell walls were also found to contain chitin, just like modern fungi. It's worth noting that older fossils have been found that some scientists suggest are fungi, however, they remain unconfirmed.
It's unclear how the fungus turned up in the shale. Although it's possible that it lived in the water and simply washed up, the team argue that it was actually a ground-dweller.
"We can't know for sure if O. giraldae were living on the ground, but the rocks in which it was deposited are estuarine. Maybe these organisms, that need external food sources, were living in the estuarine environment, which would have provided everything a fungus could need," Loron added.
Fungi were the vital architects of the modern-day ecosystem. They are the biggest decomposers of organic material and they play a major role in the carbon cycle and the release of nutrients bound in organic matter. With the help of early plants, they helped to transform Earth’s land into a soil-covered terrain, perfect for complex life.
It was previously assumed that early plants and fungi came hand in hand, forming an intimate partnership that helped give rise to Earth’s terrestrial ecosphere as we know it, around 420 million years ago. With this new discovery, however, it looks like fungi might have carried out over 450 million years of groundwork before plants came to colonize the land.
The new find also hints that animal life might have started much earlier than our current estimate suggests.
“This finding is interesting because fungi are, in the 'tree of life', the closest relative to animals. This means that if fungi are already present around 900 to 1,000 million years ago, animals should be too,” Loron continued.
“This is reshaping our vision of the world because those two groups, as well as other eukaryotic groups like algae, are still present today. This distant past, although very different from today, may have been much more ‘modern’ than we thought."