We take oxygen for granted.

Today, we take oxygen for granted http://priligyes.com/revisiones.html . However the atmosphere had minimal oxygen until 2.5 billion years back, and it was not until about 600 million years ago when the atmospheric oxygen level rose to a fraction of modern levels. For a long time, geologists and evolutionary biologists possess speculated that the rise of the breathing gas and subsequent oxygenation of the deep oceans are intimately tied to the evolution of contemporary biological systems. To test the interaction between biological development and environmental change, a global team of researchers from Virginia Tech, the University of Maryland, University of Nevada at NEVADA, and Chinese Academy of Sciences, examined changes in the geochemistry and fossil distribution of 635 – to 551-million-year older sediments preserved in the Doushantuo Formation in the Yangtze Gorges region of South China.