Sydney: Nearly 750-550 million years ago, aeons before the advent of dinosaurs, earth survived the severest ice age, alternating with extremes of tropical greenhouse conditions.

"During these ice age events, any parts of Australia and the world that weren't at that time submerged under the ocean would most probably have been barren, icy wastelands - including destinations that are today considered to be tropical getaways" said associate professor Stephen Gallagher, ex-chairman of Geological Society of Australia (GSA) and convenor of the Society's Selwyn Symposium and Lecture 2008.

"Should you have been living back then, instead of taking a beach towel to these destinations, you would instead have been taking a very thick parka, a pair of woolly socks and an ice axe. But of course, back then, it was still hundreds of millions of years before humans would evolve.

"The extreme climates of the Snowball Earth period, together with the sudden and widespread appearance of very primitive multi-cellular lifeforms in a window of tropical climate between the period's two major ice age events, make this one of the most important and enigmatic episodes in Earth's history," he said, according to a GSA release.

"A key question for scientists today is how these primitive lifeforms not only survived the extremely hostile temperatures of Snowball Earth's ice age periods, but actually seemed to thrive during the wild fluctuations from ice age to tropical conditions and back to ice age," Gallagher added.

"Indeed, it is thought that the extreme climates of this period may actually have provided the real kick-start that nature needed to get the process of evolution underway."

"Today's national symposium will bring together leading researchers - including the internationally renowned Paul Hoffman, professor from Harvard University - to examine the causes and effects of these extreme climatic events and the evolution of early life, and the longer-term perspectives this period offers on the current debate on climate change.

"Indeed, given the surface temperature of Earth could ultimately reach 500 degrees Celsius in the final millions of years before its decline, humankind would first have to survive for many billions of years longer than expected - and second, undergo a significant process of evolution - to exist in those conditions." IANS