But here we are talking rudimentary forms of life. Once life gets going natural selection in Evolutionary Theory makes it almost certain that intelligence will develop and thrive. Others argue that intelligence has not yet proven to be such a hot evolutionary advantage. Sharks are dumb and they have been around for hundreds of millions of years. Evolution works by chance.
Random mutation leads, once in a million times, to superior adaptation.
For intelligence to form you need a million million chance events. So it formed here. Why should it form elsewhere. It is interesting to note that the people who think evolution produces lots of cosmic intelligence are astronomers. Evolutionary Biologists are the ones who are most skeptical of extra-terrestrial intelligence.