A long read introduction to the topic - from We Want to Believe: How Aliens Went Mainstream and Why It Matters
“The search for exoplanets is radically expanding our understanding of the cosmos. “We have learned that the universe is teeming with a fascinating variety of planets, more types than we could have imagined,” writes the astrobiologist Lisa Kaltenegger. But so far, it has found exactly as many extraterrestrials as radio astronomy has: zero. The more we learn about the universe, the more acute the Fermi paradox becomes.”
What we consider intelligent is quite subjective
Under different definitions, “a forest” could be an inteligent individual
I knew one. He was not at all intelligent.