Researchers that include members of NAI's Arizona State University Team and NASA's Exobiology program are using the isotopic composition and concentration of molybdenum in sedimentary rocks to explore how the evolution of Earth's biota is intimately linked to the oxygenation of the oceans and atmosphere. Their results, published in PNAS, indicate two episodes of global ocean oxygenation. The first coincides with the emergence of the Ediacaran fauna ~550 million years ago, including large, motile bilaterian animals. The second, perhaps larger, oxygenation took place ~400 million years ago, well after the initial rise of animals, therefore suggesting that early metazoans evolved in a relatively low oxygen environment. [Source: NAI]
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