Fossils locked away for 1.75 billion years hold clues about key moment in Earth's history

The sun shines brightly under a forest canopy that highlights the many leaves and plants underneath.

The earliest direct evidence of photosynthesis has been discovered in fossils dating back to 1.75 billion years ago.

Scientists collected fossils from Australia, Canada and the Democratic Republic of Congo and found the samples from Australia and Canada contained evidence of cyanobacteria, the oldest known lifeform on Earth. Scientists believe that cyanobacteria first emerged 2 to 3 billion years ago, before evolving to be capable of oxygen-producing, or oxygenic, photosynthesis.