9 May 2017
Kathy Campbell, University of New South Wales
By Alice Klein
It’s the age-old question: where do we come from? New fossil evidence suggests the first spark of life may have occurred in a hot spring on land rather than a hydrothermal vent in the deep sea.
Charles Darwin proposed in 1871 that life originated in a “warm little pond”. But the dominant theory nowadays is that primitive microorganisms first assembled in hot, chemical-rich water at hydrothermal vents at the bottom of the ocean.
One reason for favouring this marine model is that fossil evidence of early land-based microbial life has been lacking. Until recently, the oldest evidence of life on land was only 2.8 billion years old, whereas the oldest evidence from the sea was 3.7 billion years old.
Now, a team led by Tara Djokic at the University of New South Wales in Australia has discovered fossils of land-based microorganisms. They were found in 3.5-billion-year-old rocks in an extinct volcano in the Dresser Formation in the hot, dry, remote Pilbara region of Western Australia.
The fossils include stromatolites – layered rock structures created by microorganisms – and circular holes left in the rock by gas bubbles that look like they were once trapped by sticky microbial substances. Both types of structures are preserved in geyserite, a type of rock that is only found in and around freshwater hot springs in volcanic areas on land.
Land-based launch pad?
The findings suggest that microbes were present on land and in the ocean around the same time, says Djokic. The question is – which came first?
“There are now a number of converging lines of evidence that point to terrestrial hot springs over hydrothermal vents for the origin of life,” says Djokic.
Small bodies of water like hot springs may have been more conducive to the formation of life because they can evaporate and concentrate the building blocks of life, says Djokic. “In hot springs, you’ve also got a nutritious concoction of elements because hot fluids circulate through the underlying rocks and bring up different minerals,” she says.
Continued
Kathy Campbell, University of New South Wales
By Alice Klein
It’s the age-old question: where do we come from? New fossil evidence suggests the first spark of life may have occurred in a hot spring on land rather than a hydrothermal vent in the deep sea.
Charles Darwin proposed in 1871 that life originated in a “warm little pond”. But the dominant theory nowadays is that primitive microorganisms first assembled in hot, chemical-rich water at hydrothermal vents at the bottom of the ocean.
One reason for favouring this marine model is that fossil evidence of early land-based microbial life has been lacking. Until recently, the oldest evidence of life on land was only 2.8 billion years old, whereas the oldest evidence from the sea was 3.7 billion years old.
Now, a team led by Tara Djokic at the University of New South Wales in Australia has discovered fossils of land-based microorganisms. They were found in 3.5-billion-year-old rocks in an extinct volcano in the Dresser Formation in the hot, dry, remote Pilbara region of Western Australia.
The fossils include stromatolites – layered rock structures created by microorganisms – and circular holes left in the rock by gas bubbles that look like they were once trapped by sticky microbial substances. Both types of structures are preserved in geyserite, a type of rock that is only found in and around freshwater hot springs in volcanic areas on land.
Land-based launch pad?
The findings suggest that microbes were present on land and in the ocean around the same time, says Djokic. The question is – which came first?
“There are now a number of converging lines of evidence that point to terrestrial hot springs over hydrothermal vents for the origin of life,” says Djokic.
Small bodies of water like hot springs may have been more conducive to the formation of life because they can evaporate and concentrate the building blocks of life, says Djokic. “In hot springs, you’ve also got a nutritious concoction of elements because hot fluids circulate through the underlying rocks and bring up different minerals,” she says.
Continued
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