Ancient Fossils Shed Light on Earth’s History: Photosynthesis Evidence Found in 1.75-Billion-Year-Old Specimens

Article: Fossils discovered in Australia are offering the first direct proof that photosynthesis occurred at least 1.75 billion years ago. The groundbreaking discovery reveals the earliest evidence of photosynthesis, as indicated by fossils dating back to 1.75 billion years ago.

Scientists, conducting research in Australia, Canada, and the Democratic Republic of Congo, uncovered fossils in Australia and Canada that contained traces of cyanobacteria, Earth’s oldest known life form. Cyanobacteria are believed to have emerged 2 to 3 billion years ago, evolving into the ability to perform oxygenic photosynthesis.

Published in the journal Nature on January 3, a study disclosed that these cyanobacteria fossils exhibited photosynthetic structures, specifically thylakoid membranes containing pigments like chlorophyll, responsible for converting light into chemical energy through photosynthesis.

Preserved in compacted mud clay that transformed into rock over time, the cyanobacteria fossils were examined using transmission electron microscopy (TEM). This technique utilizes electrons, with a significantly smaller wavelength than light, enabling the visualization of finer details down to the atomic level. By bombarding a sample with an electron beam, scientists could observe membranes and other intricate details in the fossils.

Lead author Emmanuelle Javaux, a paleobiologist from the University of Liège in Belgium, highlighted the significance of finding these membranes, stating that it extends the fossil record of such structures by 1.2 billion years.

Identifying the exact period when cyanobacteria evolved the capability to produce oxygen is a crucial milestone in Earth’s natural history. The rise in atmospheric oxygen approximately 2.45 billion years ago, known as the Great Oxidation Event, transformed life on Earth, enabling aerobic respiration and enhancing nutrient availability.

Scientists are still debating whether the Great Oxidation Event resulted from the evolution of oxygenic photosynthesis or if other ecological or geological events occurred first. The biological and physical drivers behind this event remain deeply contested among researchers.

Greg Fournier, a geobiologist at the Massachusetts Institute of Technology not involved in the study, commented on the alignment of the fossilized structures’ age with current theories about cyanobacteria with thylakoid membranes. The researchers’ use of electron microscopy opens the door to reanalyzing older fossil samples with the same technique, potentially providing insights into when cyanobacteria initially evolved thylakoid membranes.

Fournier concluded by emphasizing the potential to time these evolutionary innovations and connect them to the history of the biosphere.