A Supermassive Ice Age May Have Led to Complex Life on Earth

There was a time on Earth, about 635 million years ago, when almost the entire planet was covered in ice. At least, this is the idea underlying the Snowball Earth Hypothesis, which holds that there was a massive ice age before the proliferation of complex, multicellular life. Though it's still controversial,… » 3/04/13 10:41am 3/04/13 10:41am