Two billion years ago the Earth system was recovering from perhaps the single-most profound modification of its surface environments: the oxygenation of the atmosphere and oceans. This led to a series of major changes in global biogeochemical cycles.
Fuente : http://feeds.sciencedaily.com/~r/sciencedaily/~3/g...
Fuente : http://feeds.sciencedaily.com/~r/sciencedaily/~3/g...