Any person who is minimally aware of astronomy realizes that the Earth is one of several planets within our solar system, of which the sun is a minor star of billions of others within a spiral arm of our galaxy. This galaxy is one of countless other galaxies within the viewable universe as we know it. As our technology increases, we realize that there are other planets around other stars, and speculation is that some may have life, and a few of these life forms may be intelligent. OF COURSE! Why are we so naive to believe that this minor speck in the universe is the only possible "intelligent" life?
We are not the oldest solar system - even within our own galaxy. There are life forms which have probably been around eons before us and their technology would be far beyond our own. If we had the advanced technology for interstellar travel, we would undoubtedly be studying other life forms that we would encounter in our region of stars. Even with our current technology, which is crude at best, we are beginning to realize that there is the possibility of other life forms out in space.
To realize the complexity of life forms, we merely need to look at our own planet. There are life forms that look different from us and each other based on the adaptation to their environment. Creatures that crawl, swim, fly, or even live anchored to the ground. Many shapes and sizes from microscopic to enormous; many adaptations to food sources, some symbiotic, others predatory, but all surviving in their adapted niche. Why would that only be true on planet Earth?
Since life adapts to it's environment, we should expect that the life that exists on other planets would evolve based on various critical factors. Gravity would determine whether the creatures would be thin and tall or short and stocky, the amount of light would affect the size of their eyes (probably at least two for binocular vision) and sensitivity to the spectrum to which they are used to. Thin air would require large lungs if air breathing (dependent on the gases in the atmosphere). All sorts of adaptations are possible as we see on earth. Their skin would also be determined by factors such as radiation, etc. The end result is that we should not expect that they are even carbon based or water dependent as we are. In fact, they do not need to resemble us in any way.
For many years we have been sending radio and TV signals which radiate into space. Unfortunately, most of it is inane indicating to other intelligent life that we are primitive. Assuming that many UFO sightings are in fact ET in origin, who can blame them for being curious to study our primitive, and warring, societies without making direct contact. Our first reaction would be to try to kill or capture one for study. Fortunately, they apparently do not want the same from us.
As I said earlier, we are a primitive world, and we have barely begun to understand who, and what, we are. After all it has been perhaps 100,000 years since our prototypes crawled on this earth, and merely 100 or so years since science began to scratch the surface of technology. That is an extremely minor blip in the estimated thirteen billion years that the universe has been around.
