Researchers have found evidence that the planet may have been a "Snowball Earth" at some points in pre-historic time, and the deep freeze could have spurred the explosive diversity of life forms.

The study showed that during the Cryogenian period, the planet may have been a "Snowball Earth," coated in ice for stints lasting millions of years. These deep freeze could have spurred the evolution of animals by pumping a surge of nutrients into the oceans.

They noted that evidence also showed major groups of animals may have actually existed millions of years before the explosive diversity of life forms in the later Cambrian explosion, an event that began about 540 million years ago during the Cambrian period where there was rapid expansion in the diversity of life forms and all the major groups of animals seemed to materialize rapidly.

This burst in diversity can be the result of the evolution of the animals and their interaction with each other while the Earth was a frozen orb, reserchers said.

Analyzing the the fossil record and genomes of existing organisms that are related to Cambrian species, scientists said the results suggest that many of Earth's early organisms developed their genetic programs 635 million to 850 million years ago during the Cryogenian period. They later flourished when more favorable environments happened.

"We see that there's this long lag between the evolution of the developmental toolkits for their bodies and the explosion of diversity we see in the fossil record," said researcher Douglas Erwin, curator of paleozoic invertebrates at the Smithsonian National Museum of Natural History.

"The explanation for what happened in the Cambrian lay in how organisms modified their environment," he added.
The findings are published in the Nov. 25 issue of the journal Science.