Earth had enough oxygen before animals appeared

It's a known fact that oxygen is crucial for the existence of animals on Earth, but did you know that an increase in oxygen level did not apparently lead to the rise of the first animals.

A new research conducted by the University of Southern Denmark showed that 1.4 billion years ago there was enough oxygen for animals and yet over 800 million years went by before the first animals appeared on Earth.

Animals evolved by about 600 million years ago, which was late in Earth's history. The late evolution of animals and the fact that oxygen is central for animal respiration, has led to the widely promoted idea that animal evolution corresponded with a late a rise in atmospheric oxygen concentrations.

Researchers Emma Hammarlund and Don Canfield said that their study indicates that sufficient oxygen in itself does not seem to be enough for animals to rise.

Their analyses revealed that a deep ocean 1.4 billion years ago contained at least 4 per cent of modern oxygen concentrations.

The study is published in the journal Proceedings of National Academy of Sciences.