Previously scientists believed that sudden drastic positive change in oxygen levels in the atmosphere triggered evolution of more complex organisms like sharks and whales from simpler life forms like algae, bacteria and other microorganisms. Favouring the notion, a new study has found that a jump in oxygen level caused such drastic changes, however the rise in oxygen concentration was very mild.
A team of researchers claims that oxygen level did rise in the water and atmosphere, however the increase in concentration was at lower levels than thought previously to drive changes in lives on earth.
Benjamin Gill, an assistant professor of geoscience in Virginia Tech’s College of Science, said that Earth’s atmosphere contains nearly 21 percent oxygen , however scenario wasn’t the same in the past and nearly 635 to 542 million years ago, Earth saw 10 to 40 percent rise in oxygen level. This was also the second time when Earth saw such increment in its entire history.
For the research, study authors examined the amount of oxygen by analysing the qauntity of iron present in shale rock, which was once mud on ancient seafloors. Researchers collected rock samples from all over the globe and analysed it thoroughly. Study authors say that the amount of iron found in the rock along with its location gave them important clues about the oxygen levels and ancient water chemistry over time.
For better results, more precise study on magnitude of oxygenation and physiological requirements of early animals needs to be done which tell us more about animal evolution, said first author Erik Sperling, an assistant professor of geological and environmental sciences at Stanford University. He further added that oxygen levels have been decreasing continuously at a slow rate since past few years. Although the drop rate isn’t that significant to affect the climate directly but cumulatively it will affect the Earth and its biodiversity in next million years.
The study was published in the journal Nature.