Snowball Earth was typical
http://www.spacedaily.com/news/early-earth-01d.html
The early sun was dimmer than today, so why wasn't the Earth frozen over? Answer: it was. If so, that explains why complex multicellular life took so long to get started. The Earth's envions were inhospitable for a couple billion years here and there. Yet another reason to appreciate how RARE complex animal life is in the galaxy.
-philw (hopes there's other Earths, but wonders)