Proponents of this “Rare Earth” hypothesis also argue that the evolution of complex life requires an exceedingly large number of perfect conditions. In addition to Earth being in the habitable zone of the Sun, our star must be far enough away from the galactic center to avoid destructive radiation, our gas giants must be massive enough to sweep asteroids from Earth’s trajectory, and our unusually large Moon stabilizes the axial tilt that gives us different seasons.
It is all summed up in the above lines.
About intelligence as we know it, it is a mean of survival, it is a special case for humans, since they are the most intelligent of the intelligent life on earth, which is debatable, because we do not live in water or in the air, so intelligence is in reality a context affair. The same apply in the universe; there might be other forms of intelligence in their own perfect conditions, and geared toward survival by intelligence. In this way the stars and galaxies too are surviving with intelligence, the question is on what level, and the answer is, certainly a much higher level than ours which is the highest on earth.
The whole universe is linked somehow, take the moon and the sun for example and their influences on temperature and seasons on earth, and we know that intelligent life exists on earth because of that. So what level of intelligence are we talking about, since humans are limited in all their senses.
It sounds like intelligence in humans is a force acting on _ reprimanding_ their instincts, to behave wisely (read Intelligently) to the only end of survival, otherwise they won't survive, It acts like a moderating (in the positive sens of survival) factor forced upon humans, because they are unwise and not as sharp as other animals in their own environ in nature , so, when compared to other intelligent life on earth they are not the best survivors eventhough they might enjoy a higher level of reasoning than other animals, this higher reasoning capacity was a requirement, not a choise in order to survive. First they needed to form packs, which is instinct or strategy (sounds better) more than intelligence, since we can find the same behavior in most animals and plants surviving in packs. We notice the same phenomenon in outer space, or better yet just looking into our galaxy with every planet playing a distinct and required role for the survival of the galaxy.
This is another way of looking at intelligence and survival. So for me , evolution , survival of the fittest and the rest are micro components, depending on much more important and essential elements, in the micro as well as the macro world .
So intelligent life - as we understand it from this perspective presented here - on other planets in other circumstances can exist in their own forms if there are specific and required conditions applied to a whole galaxy or the habitable part of it like the milky way in Earth's case. But I doubt it very much that they will have a human or humanoid, animalistic or botanical like features.
it is the only way for us to imagine them (we know no other forms in our brains, and we can not imagine planets, stars and galaxies without hands or legs or heads being intelligent life), but it is not the only way for the higher intelligence running the universe.