New Oxygen research; photosynthesis early appearance? (Introduction)

by David Turell , Wednesday, January 03, 2024, 19:43 (325 days ago) @ David Turell

New fossils give a very early date or 1.78 billion years ago:

https://www.sciencenews.org/article/bacteria-fossils-oldest-machinery-photosynthesis-th...

"Ancient tiny fossils from Australia may carry evidence of great power: the ability to make oxygen through photosynthesis.

"The fossilized bacteria, dating from 1.73 billion to 1.78 billion years ago, are chock-full of structures that resemble those where oxygen-producing photosynthesis takes place in most modern cyanobacteria and in plants. Called thylakoid membranes, the structures are the oldest ever found, researchers report January 3 in Nature. The finding pushes back the evidence of thylakoids in cyanobacteria by 1.2 billion years.

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"Researchers already had indirect evidence from genetics and chemical studies that cyanobacteria had developed thylakoids by the time these fossilized bacteria lived, says Patricia Sanchez-Baracaldo, an evolutionary microbiologist at the University of Bristol in England. Still, exactly when the structures evolved is hotly debated. So it’s exciting to see fossil evidence of such old thylakoids, says Sanchez-Baracaldo, who was not involved in the work. “Any evidence that you have from that time period is important because the fossil record is really very sparse.”

"Some researchers think that thylakoids may have evolved before the Great Oxidation Event around 2.4 billion years ago. Prior to that event, there were whiffs of oxygen here and there in the atmosphere, but it took the concentrated action of photosynthetic bacteria to send Earth’s oxygen levels skyrocketing. Stacks of thylakoids within cyanobacteria may have multiplied the bacteria’s oxygen production.

"During the period when the now-fossilized cyanobacteria lived, oxygen levels in Earth’s atmosphere had plummeted again to a fraction of today’s levels, Sanchez-Baracaldo says. The fossils hint that there may have been small pockets where oxygen was abundant and could have fostered the evolution of the ancestors of plants and animals."

Comment: if oxygen dependent organism were to arise, oxygen had to come first. The very first organisms on the sea floor appeared in a highly anoxic ocean. The highly complex Cambrian forms could only appear once the oceans were oxygenated.