An international team of scientists in South China accidentally discovered the oldest terrestrial fossil, which is about three times more ancient than the oldest ancient dinosaur.
The investigation is still ongoing and the comments will need to be independently verified, but the international team argues that the long thread-like fingers of this ancient creature look like fungi.
Whatever it is, the eukaryote appears fossilized on land 635 million years ago, as if the Earth was recovering from the global ice age.
During this massive avalanche event, our planet resembled a large snowball, sealing its oceans with more than a kilometer (0.6 mi) of solid ice from the Sun. And then, in a geologic ‘flash’, our world began to melt unnecessarily, allowing life to flourish on the ground for the first time.
Fungi would have been one of the first life forms to colonize that fresh place. The date of this new microfossil certainly supports the emerging idea that some fungi-like organisms dug the oceans for life on land before plants.
In fact, this transition could be the reason that such a terrible ice age helped us to recover our planet.
“If our interpretation is correct, it would be helpful to understand change and early life development,” says geologist Tian Gun of the Virginia Tech College of Science.
Today, the early development of fungi remains a big mystery, in large part because without bones or shells, these organisms do not readily form fossils. Not too long ago, many scientists did not even think that it is possible for fungi to last long.
The genome of modern-day fungi suggests that their common ancestor lived about a billion years ago, remaining from animals at the time, but unfortunately, the first apparent fungus in our records may have been 600 million years before fossils .
In recent years, a stream of intriguing and controversial discoveries has helped bridge that gap.
In 2019, scientists reported the discovery of a fungal-like fossil in Canada, which formed a fossil in a estuary a billion years ago. The implications were huge – meaning that the common ancestor of fungi would have been much earlier than the common ancestor of plants.
In 2020, a fossil similar to the fungus was found in the Democratic Republic of Congo, and it was fossilized in a lagoon or lake 810 and 715 million years ago.
Controversy still exists as to whether these ancient organisms were actually fungi or not, and the new microfossils found in China would not doubt such a debate. After carefully comparing the characteristics of the organism to other fossils and living life forms, the authors identify that it is a eukaryote and a “potential fungus”.
“We want to leave things open to other possibilities as part of our scientific investigation,” says Virginia Tech geologist Shuhai Xiao.
“The best way to plant it is that perhaps we have not ruled out that they are fungi, but they are the best explanation we have at the moment.”
That said, the new discovery provides further evidence that organisms like fungi may already have plants on the ground.
Xiao explains, “The question was’ were there fungi in the terrestrial area before terrestrial plants grew”.
“And I think our study says yes.”
The next question is: how did that fungus survive?
Today, many species of terrestrial fungi are disabled for photosynthesis. As such, they rely on a reciprocal relationship with plant roots, exchanging water and nutrients from rocks and other hard organic materials for carbohydrates.
Because of this relationship, it was thought that plants and fungi would help together to populate the land. But the fossil of the oldest terrestrial plant dates back only to 470 million years ago.
The recently detected fungi-like microfossil is much older than that and was found hidden within small cavities of limestone dolostone rocks located in the Doushanto Formation in South China.
The rock in which the fossil was found appears to have accumulated around 635 million years ago, when our snowball melted the Earth. Once open to the elements, the authors suspect that carbonate cement began to fill in the cavities between the limestone sheets, possibly luring microbes living inside these bubbles.
These fungal-like life forms can also occur with other terrestrial microbes, which were also widespread at the time, such as cyanobacteria or green algae.
If fungi-like animals were equally ubiquitous, it is possible that these life forms helped accelerate chemical weathering, transport phosphorus into the ocean and trigger a wave of biotechnology in marine environments.
On land, they have probably helped trace soil minerals to carbon sequestration in Earth’s soil, creating a fertile environment for plants and animals and possibly altering the climate of our planet.
“Thus,” the authors conclude, “microbes such as doushuntu fungi, as they were, may have played a role in catalyzing atmospheric oxidation and biospheric evolution in the aftermath of terminal cryogenian global glaciation. “
The study was published in Nature communication.