Scientists have made a stunning discovery in Australia that could rewrite the history of life on Earth. They found ancient evidence of photosynthesis in microfossils dating back 1.75 billion years.
Photosynthesis is a process by which some organisms use sunlight to convert water and carbon dioxide into glucose and oxygen. This is essential for the survival of most life forms on Earth, as oxygen is required for cellular respiration. The origin and evolution of photosynthesis has long been a mystery. Scientists have debated when and how the first organisms developed the ability to carry out oxygenic photosynthesis, which is unique to cyanobacteria and their descendants.
Cyanobacteria are also known as blue-green algae and are among the oldest and most diverse groups of bacteria. They played a pivotal role in shaping Earth’s biosphere, as they were responsible for the Great Oxidation Event, which occurred around 2.4 billion years ago and dramatically increased oxygen levels in the atmosphere.
A team of researchers from the University of Sydney and the Australian National University has identified fossilized structures of Navisifusa majensis, a type of ancient cyanobacterium, among 1.75 billion year old microfossils in the McDermott Formation, a geological site in northern Australia.
This is the oldest direct evidence of oxygenic photosynthesis ever found and challenges previous assumptions and timelines about the evolution of this process.
This discovery shows that oxygenic photosynthesis existed much earlier than previously thought and was more widespread and diverse than previously assumed.
The researchers used a variety of techniques, including electron microscopy and spectroscopy, to analyze the microfossils and confirm their identity and age. They also compared them to modern cyanobacteria and found striking similarities in their biochemistry.
This discovery is important for our understanding of the early history of life on Earth and the atmospheric conditions that made it possible.
The fossil structures found are called thylakoids, which contain pigment molecules and proteins that capture and convert light energy. Thylakoids are key components of the photosynthetic machinery in cyanobacteria and plants.
By analyzing the microfossils, the researchers were able to detect chlorophyll, the main pigment molecule in photosynthesis, and iron, which is involved in electron transport. They also used a technique called electron microscopy to create high-resolution images of the fine samples.
By measuring the ratio of uranium to lead in the rocks, they were able to determine that the fossils were 1.75 billion years old.
The discovery also raises new questions about the origin and evolution of photosynthesis, given that oxygen levels in the atmosphere and oceans may have fluctuated more than previously thought and environmental conditions may have been more variable.
This discovery also demonstrates the importance of curiosity and exploration, as researchers were inspired by the previous discovery of similar fossils in Canada and decided to look for them in Australia.
Cover Photo: Patrick T. Fallon