Not too long ago we visited "Snowball Earth," a period when most of the planet's land was covered by glaciers between 750 and 635 million years ago, and we concentrated on how it was a kind of runaway global warming that finally brought the icy era to an end.
But the warming may have done a lot more than that. By melting the glaciers, it may have kick-started life as we know it.
The line between the PreCambrian and Cambrian eras, about 600 million years ago, is marked by what is called the "Cambrian Explosion" - suddenly, all over the world, the fossils of countless brand-new creatures began showing up. And, in a mere 85 million years or so, animals evolved and radiated over much of the world's land and oceans. What made this possible?
Scientists have long suspected that the melting of the glaciers, which had dragged along nutrients scraped from the Earth's surface and now was releasing them into the sea, had provided enough food like phosphorus to spur a huge algae growth. The algae, in turn, would have given off enough oxygen to allow the quick spread of air-breathing animals.
But for years, there was little proof of this. Now, however, scientists have figured out how to use iron-rich deposits from ancient, low-oxygen oceans to estimate how much phosphorus was in the water. (Iron scavenges phosphorus is a predictable way.) It turns out phosphorus spiked at just the right time.
Gosh ... yet another reason to thank at least one episode of global warming.