Before animals, evolution waited eons to inhale
http://phys.org/news/2016-07-animals-evolution-eons-inhale.html
A couple of times in four billion years, evolution has slowed to a crawl.
And an eon or so has passed before more complex life forms, such as simple animals, could arise.
Evolution may have been waiting for a decent breath of oxygen, said researcher Chris Reinhard. And that was hard to come by.
His research team is tracking down O2 concentrations in oceans, where earliest animals evolved.
By doing so, they have jumped into the middle of a heated scientific debate on what rising oxygen did, if anything, to charge
up evolutionary eras. Now, Reinhard, a geochemist from the Georgia Institute of Technology, is shaking up conventional thinking
with the help of computer modeling.
![](http://cdn.phys.org/newman/csz/news/800/2016/beforeanimal.jpg)