>>9829562
Assuming life on earth arose through abiogenesis, it's possible that such a natural occurrence is extremely rare, a statistical improbability, and that life evolving intelligence is even rarer
It's estimated that there are 100 billion planets in the Milky Way, but it would not surprise me at all if the planets with intelligent life only number in the tens or hundreds, and are so far apart that lifeforms from different planets never come into contact with each other
Not that this speculation means much, since we only have a sample size of 1 inhabited planet at the moment