THE case for the existence of photosynthetic life 3.4 billion years ago has been significantly strengthened. The new evidence, which comes from a layer of carbonaceous rock in South Africa, is certain to fuel the controversy about when exactly such life began on Earth.
In 2002, Martin Brasier from the University of Oxford and his colleagues disputed claims that microscopic patterns found in 3.5-billion-year-old rock in Western Australia were microfossils of various bacteria, including photosynthetic cyanobacteria. Brasier claimed the fossils were really patterns formed during the recrystallisation of volcanic glass from a hydrothermal vent that formed tens of metres under water - too deep for photosynthetic bacteria to live.
Similar questions were raised about a 3.4-billion-year-old layer of carbonaceous rock found in the Buck Reef Chert in South Africa. The chert was once a volcano in the sea that sank into the Earth's crust as it cooled. Billions of years ...
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