We take oxygen for granted.
Today, we take oxygen for granted. But 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 http://www.sildenafilcitrate.net/ed-pills/ . For a long period, geologists and evolutionary biologists have got speculated that the rise of the breathing gas and subsequent oxygenation of the deep oceans are intimately tied to the evolution of modern biological systems. To check the conversation between biological evolution and environmental change, an international team of scientists from Virginia Tech, the University of Maryland, University of Nevada at Las Vegas, and Chinese Academy of Sciences, examined adjustments in the geochemistry and fossil distribution of 635 – to 551-million-year previous sediments preserved in the Doushantuo Formation in the Yangtze Gorges region of South China.