Nevertheless the progress on the other factors in the Drake equation is very interesting and impressive.
I disagree with this.
It seems that, from what happened to other planets on the solar system, that nothing happened on Earth too much out of the ordinary. Mars had a similar story (except for the whole Moon coming out of a giant collision), and had water. But maybe it was too small to keep warm for enough time
Earth had 5 mass-extinctions, that "reset the game" before we got to humans. Doesn't seem too far fetched to me
I really don't buy that Earth is one in a billion unless Mars is one in a billion as well. Maybe one in 1000? One in 100000?
And that's limiting intelligent life to what we know. Yes, maybe the ideal speed of chemical reactions (for intelligent life) happen around 273K, or maybe there's another way
Anyway, what reason do we have to believe that Earth is special 2X? That we happened to have the right conditions plus some randomness occurred against all odds that gave rise to life? Why is that a rational proposition?
We know the chemical elements and processes that give rise to life, and we know why Earth is a suitable place. I suggest that, given the right (e.g. Earth-like) conditions, formation of life is not only more likely than the existence of the conditions, but the formation of life may even be likely overall. Hawking has expressed this possibility. [0]
There is fossil evidence suggesting that some forms of life existed on Earth as few as 500 million short years after it was formed. So, what are the odds that one astronomically improbable event (creation of a hospitable environment) was followed in such a short period by another alleged astronomically improbable event (abiogenesis)?
But it takes a lot of time to get to "life" as we know it.
(Now the right conditions are probably not what you have on Earth today except in a couple of places)
Life on Earth is at least 4Bi y.o. http://newsroom.ucla.edu/releases/life-on-earth-likely-start...