Compelling stuff
I have to comment on with what Deep Thought Enzyme said about life on Earth being essentially single celled for several billion years...

It's also mind boggling to think that if you went back in time to the beginning of life on Earth, you wouldn't be able to breathe the atmosphere - which consisted of CO2, Ammonia and other unbreatheables. Life has in effect terraformed the planet so that virulent life can exist... and life itself seems to reap the rewards by proliferating.

*edit* (sorry!)

The idea of randomness in evolution isn't necessarily correct.... For example, there is evidence of a "genetic memory" so to speak, the example I'll cite (as I heard on Radio 4 a few weeks back) is of people who'd suffered from tuberculosis and subsequently produced children who are no better able to cope with the disease. However, their grandchildren often inherit immunity.
(Bicycle Repairman "you're also a bit of a wanker", Thu 17 Jul 2008, 10:43, Reply)