A group of international scientists operating in the Canadian Arctic claim to have discovered the oldest known fungus fossil on the planet. The specimen — named Ourasphaira giraldae — is estimated to be around one billion years old, which significantly predates the current record held by a Scottish specimen thought to be around 407 million years old.
The tiny fossilized organisms were discovered in shallow water shale which formed over millions of years in the Northwest Territories. If the find can be validated, this fungus, which existed hundreds of millions of years before complex life forms, could remould our understanding of how life evolved on land.
Exceptional preservation left key fungus features intact
This ancestor of present-day mushrooms, mold, and yeast was buried under solidified mud, protecting it from exposure to oxygen which would have caused it to decompose. In the process of studying the fossil, the team identified multicellular branching filaments with spherical spores at their ends which connect them (these components make up the mycelium).
The quality of preservation was such that the researchers were even able to identify traces of chitin — a compound found in the cell walls of fungi — using a light-based technique known as Fourier-transform infrared spectroscopy.
“The preservation is so good that we still have the organic compounds,” says lead author Corentin Loron.
Life’s advent on land is thought to have happened around 430 million years ago via some pioneering plants that moved up from the oceans. Fungi would have been an essential part of this migration, as they are in charge of processing dead organic matter and redistributing nutrients into the ground which aids the growth of new plants.
This discovery suggests that the fungi may have actually led the process hundreds of millions of years ahead of time, but questions remain around how they survived since, as far as we know, the plants they need to feed on didn’t arrive till much later. Some proposed theories about what they snacked on include algae and bacteria, which may have existed on land as far back as 3.2 billion years ago.
Scientists previously knew that fungi’s ‘molecular clock’ — the mutation rate of biomolecules in DNA which gives insight into the history of an organism — indicated that they appeared around a billion years ago, but it wasn’t until this discovery that hard evidence existed to corroborate the idea.
Fungi and animals have a closely tied evolutionary relationship, so this research also opens up questions about when the first animals appeared. If fungi were on land this far back, it’s possible that rudimentary animals may have been too. The oldest known animal fossil (of an ancient sponge species) dates to 635 million years ago.
“This is reshaping our vision of the world because those groups are still present today,” says Loron. “Therefore, this distant past, although very different from today, may have been much more ‘modern’ than we thought.”