A stepping-stone for oxygen on Earth

For most terrestrial life on Earth, oxygen is necessary for survival. But the planet's atmosphere did not always contain this life-sustaining substance, and one of science's greatest mysteries is how and when oxygenic photosynthesis first began. Now, geobiologists have found evidence of a precursor photosystem involving manganese that predates cyanobacteria, the first group of organisms to release oxygen into the environment via photosynthesis.http://feeds.sciencedaily.com/~r/sciencedaily/~3/J...