Before humans, the world was a very different place. Our planet didn’t always look the way it does now. It’s gone through some incredible changes over the past 4.5 billion years—and they’re even wilder than you’ve imagined.

If you could step back in time and stand on the Earth millions of years ago, you wouldn’t just see a few different animals. You’d see an alien planet pulled straight out of a science fiction story.

[Read the full article at Listverse.]