Stromatolite: evidence for early oxygen generation

Cynobacteria (blue algae) are among the first recorded forms of life. They were preserved as fossils in 3.5 billion year-old sedimentary rocks. Stromatolites are the most impressive form cynobacteria can take. Layers and layers of cynobacteria produced large, pillow-shaped formations. Through photosynthesis, the bacteria were able to use sunlight to convert water and carbon dioxide into life-supporting energy. Thus, oxygen was generated - for the first time - as a waste product.