2.4 Billion-Year-Old Fungus Could Rewrite Our Evolutionary Heritage

These filaments could be from an ancient fungus. Curtin University

An Australian geologist might have just made a fossil discovery that could forever change the evolutionary tree of life. While examining hardened lava formations found 2,625 feet below South Africa's Northern Cape, Birger Rasmussen from Curtin University noticed strange vesicles in the basalt, signatures of fossilized fungi.

"I was looking for minerals to date the age of the rock when my attention was drawn to a series of vesicles, and when I increased the magnification of the microscope I was startled to find what appeared to be exquisitely preserved fossilized microbes," said Rasmussen, reports SciMix. "It quickly became apparent that cavities within the volcanic rocks were once crawling with life."

Finding fossils in and of themselves might not seem so remarkable, but when you consider that these fossils were found in rocks dated to 2.4 billion years, it gets exciting. To put things in perspective, the oldest fossilized fungi ever found previous to this discovery are just 385 million years old. That makes Rasmussen's discovery older by 2 billion years.

A find like this, if the fossils are confirmed to be ancient fungi, is sure to shake up the evolutionary history of fungi, but it could also shake up the story of life as we know it on the whole. That's because fungi are eukaryotes, the biological classification for all organisms that have cells with a membrane-enclosed nucleus (humans included), and the oldest eukaryote fossil ever found is "only" 2.1 billion years old. That means that Rasmussen's discovery could also represent the oldest eukaryote ever discovered.

The other startling aspect of this find is that the rocks where the fossils were found were formed deep underwater. It was previously believed that the first fungi must have evolved on land, but this discovery would obviously throw shade on that theory. It opens up a whole new window for investigation. Perhaps the reason that no other fossil fungi have been found that date to before 385 million years ago is because scientists have been looking in the wrong places for them.

"This would have tremendous implications for the lifestyle of the early ancestors of eukaryotes and fungi," Rasmussen told AFP.

More eyes will be needed to study the microfossils to definitively confirm that they are fungus-like, and that they have been dated accurately. But early indications all point to the fossils being genuine.

The finding was reported in the journal Nature Ecology and Evolution.