Researchers from the Swedish Museum of Natural History uncovered the fossils of what appears to be a 2.4-billion-year-old fungus preserved inside ancient basaltic rocks in South Africa.
The fossil samples were recovered from the ancient basalt of the Ongeluk Formation, in the vicinity of the Northern Cape Province.
These rocks were once found beneath the sea floor, having been formed by lava flowing under the sea bed.
The scientists who made this surprising archaeological discovery suggest these fossils could in fact be the world's oldest fungus — preceding the next-oldest fungus specimen by 2 billion years.
The Oldest Fungus Fossils In The World
The samples drilled out of the ancient rocks resemble living fungi and, despite being much older, are almost identical with fossils unearthed from similar land environments.
The fossils are made up of mycelia filaments no wider than hundredths of a millimeter (1 mm is equivalent to 0.03 inches), that "branch and anastomose, touch and entangle each other," document the researchers.
The team, led by Professor Stefan Bengtson, detailed their discovery in the journal Nature Ecology & Evolution.
The researchers believe these fungi may have colonized cavities of volcanic rock deep beneath the sea floor. They suggest that fungi arose not on land but in the deep sea — which is where science should have looked for the oldest fossil fungi all along, instead of on land or in shallow seas.
"The deep biosphere (where the fossils were found) represents a significant portion of the Earth, but we know very little about its biology and even less about its evolutionary history," said Bengtson in a statement for BBC News.
According to his study, the Ongeluk fossils "are indistinguishable from mycelial fossils found in similar deep-biosphere habitats in the Phanerozoic," which the researchers show were identified as fungi based on "chemical and morphological similarities to living fungi."
Although the habitat from where the specimens were retrieved "is at least 400 million years old," the Ongeluk discovery "suggests that life has inhabited submarine volcanics for more than 2.4 billion years."
Bengtson's team reports the newly discovered fossils are "two to three times older than current age estimates" of the fungus fossil record.
"Unless they represent an unknown branch of fungus-like organisms, the fossils imply that the fungal clade is considerably older than previously thought, and that fungal origin and early evolution may lie in the oceanic deep biosphere rather than on land," write the authors in their paper's abstract.
Challenging The Theory Of Early Life Evolution On Earth
The importance of this remarkable find lies in its potential to substantially change the generally accepted timeline of early evolution on our planet.
If confirmed, the discovery could alter "our sense of the timetable of evolutionary history," said Andrew H. Knoll, natural history professor at Harvard University.
Nevertheless, Knoll is skeptical about the timeframe proposed by the Swedish researchers.
According to Seeker, since fungi belong to the eukaryote family — a group of early organisms that have evolved a complex cell structure for which they require oxygen — fungus-like eukaryotes living 2.4 billion years ago "would have been using oxygen at nearly the same time scientists think oxygen first appeared in notable amounts on the planet."
Knoll argues that a more plausible theory would place the earliest fungi about 1.5 billion years later than the organisms uncovered by the Swedish Museum of Natural History.
Equally skeptical, Doug Erwin, curator of Paleozoic invertebrates at the Smithsonian National Museum of Natural History, stated that the recent discovery, if proven accurate, "would significantly precede fossil evidence and molecular clock analysis for the origin of eukaryotes, much less the origin of fungi."
However, study co-author Magnus Ivarsson pointed out that the habitat in which the fungi dwelled while they were still alive would have been an extreme environment devoid of sunlight.
"Fungi in this environment most probably lived in symbiosis with microbes utilizing chemically stored energy for their metabolism," he explained. "They may not even have needed free oxygen," Ivarsson added.
This is this year's second major discovery in the field of ancient evolution by the Swedish Museum of Natural History. Last month, Tech Times reported that another team, also led by Bengtson, discovered fossil plants estimated to be 1.6 billion years old, which the researchers claimed pre-date any other similar specimens by 400 million years.