Six hundred out of billions upon billions is a conservative figure. It's simply a high probability, but - of course - says nothing about what state of development such life would be at on the life supporting planets.
You could look at it as "the lottery of the universe." How many lotteries are run every year? How many people buy tickets? What is the % of ticket holders who won?
There is a science to the Law of Probability. I just don't know what the facts about it are, but obviously it has to do with pure numbers, and the occurrence of random chance within such massive numbers.
Char :)
And that's why there are SO my suckers buying Lotto tickets!
What a scam!
Take in X amount and pay out about 40% of it!