"Enough time" can easily be longer than the age of the universe. A million monkeys typing on keyboards will eventually write shakespeare. But it will be longer than the universe before they even type a single sentence of it correctly.
You are postulating the existence of only a single universe, ours. But there could be any number of universes, and so far we have no scientific way of testing that. The anthropic principle and the possibility of multiple universes puts all probabilistic arguments to dust: anything with non-zero probability happens in an infinite number of universes.
> A million monkeys typing on keyboards will eventually write shakespeare. But it will be longer than the universe before they even type a single sentence of it correctly.
All it takes is _one_ tiny selection force to blow this argument out of the water. For example, if only _a single_ correct letter is retained from each attempt, the problem gets exponentially easier with every iteration, making the expected time to generate any work linear in its length.
I agree with you completely about the anthropic principle. But we are talking about the probability of aliens. If the anthropic principle is true, then we should expect aliens to be really really unlikely.
It sure can be, but as long as it is less than the expected lifetime of the universe it will still happen. A million monkeys - given that Hamlet contains such long sentences as "He." it will take far less then a minute for them to type a single sentence correctly.