The Origins of Oxygenic Photosynthesis Photosynthesis, in its earliest form, likely emerged around 3.5 billion years ago as anoxygenic photosynthesis, a process that did not produce oxygen.

Aerobic Anoxygenic Phototrophic (AAP) Bacteria: A group of bacteria that can use light energy for growth but do not produce oxygen during photosynthesis. Bacteriochlorophyll: A pigment found in ...