Although it was more than 4½ billion years ago that planet Earth formed, it was just a few hundred million years later, at most, that life arose on our world. For all the years since then, it’s thrived and evolved, enabling it to find a way to exist in practically every environmental niche that Earth possessed.
But 2 billion years after Earth first took shape, life almost ended. The atmosphere had slowly been altered by the gradual addition of oxygen, which proved to be fatal to the most common type of organism present on Earth at the time. For hundreds of millions of years, the Earth entered a horrific ice age which froze the entire surface: known today as a Snowball Earth scenario. It was a disaster that almost ended life on Earth entirely. Here’s the story of our near-death and ultimate survival.