https://www.smithsonianmag.com/smart-news/scientists-uncover-earliest-fossil-evidence-of-photosynthesis-180983534/

...
In a new study published Wednesday in the journal
Nature, researchers have found cyanobacteria
fossils from around 1.75 billion years ago that
seem to have had the tools to make oxygen. They
contain thylakoid membranes, structures in which
photosynthesis takes place. The find marks the
earliest fossil evidence of photosynthesis.

“This discovery extends the fossil record of such
internal membranes by at least 1.2 billion years,”
study co-author Emmanuelle Javaux, a biologist at
the University of Liège in Belgium, tells Gizmodo’s
Isaac Schultz.

Indirect evidence from genetics and chemical
studies had previously suggested that
cyanobacteria had thylakoids by this time. But
exactly when the photosynthesizing structures first
evolved remained unclear, Kevin Boyce, a
paleobotanist at Stanford University who was not
involved in the work, tells New Scientist’s Grace
Wade. The new study, he adds, indicates that this
occurred at least 1.75 billion years ago.
...


https://www.nature.com/articles/s41586-023-06896-7
Published: 03 January 2024
Oldest thylakoids in fossil cells directly evidence
oxygenic photosynthesis

Abstract
Today oxygenic photosynthesis is unique to
cyanobacteria and their plastid relatives within
eukaryotes. Although its origin before the Great
Oxidation Event is still debated1,2,3,4, the
accumulation of O2 profoundly modified the redox
chemistry of the Earth and the evolution of the
biosphere, including complex life. Understanding
the diversification of cyanobacteria is thus
crucial to grasping the coevolution of our planet
and life, but their early fossil record remains
ambiguous5. Extant cyanobacteria include the
thylakoid-less Gloeobacter-like group and the
remainder of cyanobacteria that acquired thylakoid
membranes6,7. The timing of this divergence is
indirectly estimated at between 2.7 and 2.0
billion years ago (Ga) based on molecular clocks
and phylogenies8,9,10,11 and inferred from the
earliest undisputed fossil record of
Eoentophysalis belcherensis, a 2.018–1.854 Ga
pleurocapsalean cyanobacterium preserved in
silicified stromatolites12,13. Here we report the
oldest direct evidence of thylakoid membranes in
a parallel-to-contorted arrangement within the
enigmatic cylindrical microfossils Navifusa
majensis from the McDermott Formation, Tawallah
Group, Australia (1.78–1.73 Ga), and in a
parietal arrangement in specimens from the
Grassy Bay Formation, Shaler Supergroup, Canada
(1.01–0.9 Ga). This discovery extends their fossil
record by at least 1.2 Ga and provides a minimum
age for the divergence of thylakoid-bearing
cyanobacteria at roughly 1.75 Ga. It allows the
unambiguous identification of early oxygenic
photosynthesizers and a new redox proxy for
probing early Earth ecosystems, highlighting the
importance of examining the ultrastructure of
fossil cells to decipher their palaeobiology and
early evolution.

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