A thick, green carpet of photosynthetic life, on the scale of that seen today, exploded across Earth 850 million years ago - much earlier than thought - a new study suggests.rnThe matting - a mixture of algae, mosses and fungi - would have fixed atmospheric carbon into the soil, which would then have washed into the seas for burial, according to the study (L. P. Knauth & M. J. Kennedy Nature doi: 10.1038ature08213; 2009). With lower levels of carbon to react with, global levels of oxygen would have risen. The greening of ancient Earth could thus be indirectly responsible for the sudden evolution, beginning about 600 million years ago, of larger respirating animals with oxygen-hungry cells, say geologists Paul Knauth of Arizona State University in Tempe and Martin Kennedy of the University of California, Riverside.rn"This is a profound event," says Kennedy. "It explains the rise of oxygen, and the timing of that rise."
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