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Which came first: complex life or high atmospheric oxygen?

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We and all other animals wouldn’t be here today if our planet didn’t have a lot of oxygen in its atmosphere and oceans. But how crucial were high oxygen levels to the transition from simple, single-celled life forms to the complexity we see today?

We and all other animals wouldn’t be here today if our planet didn’t have a lot of oxygen in its atmosphere and oceans. But how crucial were high oxygen levels to the transition from simple, single-celled life forms to the complexity we see today?

A study by UC Berkeley geochemists presents new evidence that high levels of oxygen were not critical to the origin of animals.

The researchers found that the transition to a world with an oxygenated deep ocean occurred between 540 and 420 million years ago. They attribute this to an increase in atmospheric O2 to levels comparable to the 21 percent oxygen in the atmosphere today.

This inferred rise comes hundreds of millions of years after the origination of animals, which occurred between 700 and 800 million years ago.

Read more at University of California – Berkeley

Photo: By measuring the oxidation of iron in pillow basalts from undersea volcanic eruptions, UC Berkeley scientists have more precisely dated the oxygenation of the deep ocean, inferring from that when oxygen levels in the atmosphere rose to current high levels.  CREDIT: National Science Foundation