Odds of intelligent life occuring?

[ignoramus]

I'd agree with you but would just like to add that the increasing complexity of the environment and the development of intelligence would drive one another.

As intelligence is a wonderful aide to survival, how could it not evolve in a world governed by natural selection, which must occur wherever there is life?

But why only 1?
I'd love nothing more than to ask my cat why he bites the fuck out of me when he's happy?

I think it's just pot luck. Mutations at the right time on the right species. Just a mutation. That's our claim to fame. And we took advantage of it naturally.