Oxygen is considered vital to the survival of life on Earth, but recently scientists found an increase in oxygen content of Earth just does not explain the appearance of the first animals. This study shows that about 1.4 billion years ago there was enough oxygen for the life of the animal, more than 800 million years before the first animals appeared on Earth.According to Emma Hammarlund postdoc and Professor Don Canfield, said that the Earth's oxygen levels provided apparently not enough for the animal to thrive. Their research in collaboration with colleagues from the China National Petroleum Corporation and the University of Copenhagen, Hammarlund and Canfield have analyzed sediment samples from Xiamaling Formation in China. And the analysis has revealed that in the oceans about 1.4 billion years ago there were at least 4% of modern oxygen concentration. The results of this study were published in the journal Proceedings of the National Academy of Sciences.
Increased Levels of Oxygen Earth
It is estimated, animals evolved about 600 million years ago and is considered to appear later in Earth's history. The ultimate evolution of animal species explain the fact that oxygen is central to the respiration of animals, where this results in widespread idea that animal evolution related to the period end increased concentrations of oxygen in the atmosphere.
Oxygen levels Earth
Many studies have difficulty in determining the oxygen concentration of the past. It combines several approaches to break new ground in understanding the oxygen concentration that occurred about 1.4 billion years ago. Scientists use the distribution of trace metals to show that the waters where the formation of sediment deposited Xiamaling already contains oxygen. Distribution of biomarkers, molecules derived from ancient organisms, it indicates that the intermediate depth waters do not contain oxygen. Therefore, formation Xiamaling buried in the oxygen minimum zone of the ancient period, similar to that currently found off the coast of Chile and Peru.
The scientists used a simple ocean models to estimate the minimum concentration of oxygen in the atmosphere needed to reproduce the distribution of oxygen in Xiamaling Formation. According to Canfield, a column of water having an oxygen concentration of at least 4% of the current atmospheric level, this situation should be enough for the animal to thrive. Such a simple way Sponge (sponges) and worms, is now able to develop Atmospheric Present Levels (PAL) is less than 4% even much less. Sponge may resemble some of the first animals on Earth, if these species evolved to 4% of the oxygen content of Earth, it is likely that the first animals may also develop with the same concentration or maybe even less than this value.
So why then the animals are not growing and late in Earth's history? Diversification of animals suddenly may be a result of various factors. Perhaps an increase in the oxygen content of Earth do not so much concerned with animal revolution, as assumed.
Reference
Enough oxygen long before animals rose 04 Jan 2016 by University of Southern Denmark via EurekAlert
Journal Ref: Sufficient oxygen for respiration animal 1,400 million years ago. Proceedings of the National Academy of Sciences, 2016; 201523449 DOI: 10.1073 / pnas.1523449113
Earth's atmospheric gases scatter blue light, image courtesey of NASA Earth Observatory
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