Sure, the probability is 1.0 given infinite time. It took 4.5 billion years for us to get here, and we didn't get started until 5 million years ago. That mean

Sure, the probability is 1.0 given infinite time. It took 4.5 billion years for us to get here, and we didn't get started until 5 million years ago. That means Earth went through 99.89% of its existence with no intelligent life. Also, Earth has had numerous extinction events that killed off at least 3/4 of land-based life (and 96% of marine life). We have no way of knowing whether extinction events are more, or less common on other habitable planets, or whether such events might even be necessary for the evolution of intelligent life.