History books describing how life on Earth developed may need to be rewritten, thanks to the accidental discovery of fossilised remains of ancient fungi.
Researchers were examining samples taken from drill-holes of rocks buried deep underground, when they found the 2.4 billion-year-old microscopic creatures.
They say they could be the first fossil traces of the branch of life which humans belong to ever unearthed.
They are believed to contain the oldest fungi ever found and could be the earliest evidence of eukaryotes – the ‘superkingdom’ of life that includes plants, animals and fungi, but not bacteria. It was believed that fungi first emerged on land, but the newly-found organisms lived and thrived under an ancient ocean seabed.And the dating of the find suggests that not only did these fungus-like creatures live in a dark and cavernous world devoid of light, but they also lacked oxygen.
Dr Birger Rasmussen, a geology professor at Curtin University in Bentley, Australia was examining lava samples to determine their age when he made the discovery.
The ancient fungus-like life forms were found in fossilised gas bubbles 800 metres (2,600 feet) underground, taken from the Ongeluk Formation in South Africa’s Northern Cape Province.
They are believed to be the oldest fungi ever found by around 1.2 billion years and could change our understanding of the timeline of the evolution of early life on the planet.
Earth itself is about 4.6 billion years old and the previous earliest examples of eukaryotes – the ‘superkingdom’ of life that includes plants, animals and fungi, but not bacteria – dates to 1.9 billion years ago.
That makes this sample 500 million years older and, if verified as both fungal and multicellular, the earliest ever discovered.
It had long been assumed that fungi first emerged on land, but the newly-found organisms lived and thrived under an ancient ocean seabed – tucked in the crevices of volcanic rock.
Dr Rasmussen said: ‘My attention was drawn to a series of petrified gas bubbles, and when I increased the magnification of the microscope, I was startled.
‘(The bubbles) were filled with hundreds of exquisitely preserved filaments that just screamed ‘life’.
In his analysis Dr Rasmussen also realised that the surrounding lava was not 2.2 billion years old, as previously thought, but 2.4 billion years old.
That extra 200 million years was significant because it straddles a critical threshold in Earth’s geological history called the Great Oxidation Event – a rapid and massive outpouring of oxygen into the atmosphere.
The new dating meant that not only had these fungus-like creatures lived in a dark and cavernous world devoid of light, but they also lacked oxygen.
For many years, fungi were grouped with, or mistaken for plants.
Not until 1969 were they officially granted their own ‘kingdom’, alongside animals and plants, though their distinct characteristics had been recognised long before that.
Yeast, mildew and molds are all fungi, as are many forms of large, mushroom-looking organisms that grow in moist forest environments and absorb nutrients from dead or living organic matter.
Unlike plants, fungi do not photosynthesise, and their cell walls are devoid of cellulose.
The creatures unveiled in the new study existed in what is called the deep biosphere, beneath land and sea.
Earlier research has turned up evidence that gas bubbles in lava below the bottom of the sea provided living space for fungi as far back as 50 million years.
Fungi in this environment most probably live in symbiosis with microbes, using chemically stored energy for their metabolism, added co-author Magnus Ivarsson, an expert on these hidden worlds.
The full results of the study were published in the journal Nature Ecology & Evolution.
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