World’s Oldest Fungus Fossils Found
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Which came first: the foot or athlete’s foot? OK, that was too easy — fungus beats feet by a mile. Here’s a tougher one. When did the first fungus appear on Earth? If you said “400 million years ago,” you were right … until a new study came out this week out in Nature Ecology & Evolution that potentially puts the birth of the first fungus at 2.4 BILLION years ago. Did you say “This could change everything”?

The deep biosphere—which hosts a significant part of Earth’s biomass—is very poorly known, and its history even more so. What we have now found is that such a habitat existed already more than two billion years ago—at a time when fungi were not thought to have yet existed.

Lead author Stefan Bengtson, a palaeobiologist at the Swedish Museum of Natural History, describes the exciting discovery by Birger Rasmussen, a professor at the Western Australian School of Mines. Rassmussen was examining ancient submarine lava from Northern Cape Province, South Africa, when he was “startled” to find microfilaments in millimeter-sized petrified gas bubbles. That wasn’t what he was looking for, but he knew that fungus fossils had previously been found in gas bubbles and determined that’s what these microfilaments were.

Fossilized microfilaments inside a gas bubble 0.8mm in diameter

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But not just any fungus fossils … 2.4 billion-year-old fungus fossils in microscopic filament bundles that resembled brooms. That’s the age of the lava Rasmussen was studying – lava that came from bedrock 2,600 feet (800 meters) deep. That’s an age that makes skeptical scientists go “hmmm.”

Why? Up until now, previous geological evidence for fungi only went as far back as about 400 million years ago. In fact, the earliest known fossils of any living creature – plants, animals and fungi – date back to 1.9 billion years ago. These new fossils pre-date that and — even more shocking – pre-date the Great Oxygenation Event which is believed to have occurred 2.3 billion years ago when the first dioxygen (O2) was dispersed into the atmosphere. That means these fungus-like life forms most likely existed deep below the sea rather than on land – another assumption this discovery has altered.

Gas bubbles inside the lava rock

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“Fungus-like” is the term used by the researchers for now because the bundles of filaments look like other fungus fossils but they don’t have definitive proof. If and when they do and these 2.4 billion-year-old fossils are identified as both fungal and multicellular, they will become the earliest known specimens of the same branch of life humans belong to.

It also means that researchers need to spend more time looking in the deep biosphere for a better picture of life on Earth 2.4 billion years ago and earlier.

However, even if you live in the sub-basement, you can’t put off cleaning the stuff growing in your shower by claiming it’s part of the “deep biosphere.”