I find this particularly intriguing because of the perspective it gives to the awesome scale of evolutionary time.
The hypothesis was first put forward by Joseph Kirschvink in the early 1990s, but given a major heft by the researches of the obsessive Paul F. Hoffman.
To contemplate the abysses of geological time is quite a heady experience in itself. But the thought that life on earth consisted of nothing but unicellular slime for over 1,000 million years (1 American billion) is OSSUM!
The almost completely frozen globe is supposed to have provided the necessary environmental conditions for some ruthless natural selection, which gave rise to the first multi-cellular organisms.
Anybody out there informed enough to debate the pros and cons? (Anybody want to speculate from a religious position why God took so much time to work out how to make organisms a bit more complex than one cell at a time?)
https://en.wikipedia.org/wiki/Snowball_Earth
