How come in almost all sifi aliens look more or less just like we do?
Well to start with you have to think who is making these fantastic stories, and the answer is us humans. It is much easier to relate to something that looks like a human, so that has a lot to do with how sifi writers and artists create these otherworldly beings. I have always been of the mindset that if we ever met someone from another planet they would be the most bizarre creature we could ever imagine, but it is easier to create something that looks mostly humanoid. Whether it was intentional or unintentional these artists and writers may be on to something.
“I would think that there’s a good chance that intelligent alien life evolved in more or less the same way and would thus bear some resemblance to humans,” says Kasting. “Not necessarily a close resemblance, though.” James Kasting, a distinguished professor of Geoscience at Penn State University.
That is a quote from the article posted below. There are a few different theories to help explain why aliens may indeed look like us, or humanoid. One is that either some DNA is prevalent throughout the universe and is seeding planets all across the cosmos, so in a roundabout way the same building blocks could yield similar results on other planets. The question then is where did this DNA come from, was if from an alien civilization or is it just naturally occurring in the universe. That is a pretty big mystery and one that if we ever find an answer could tell us where we came from. The other thing that the article talks about is bilateral symmetry, which means that if you cut something in half it is the same on both sides. If you cut a human in half right down the middle you have one eye on each side, one hand, one leg, internally is a different story but that does not seem as important. The article goes on to talk about how this seems like the most viable outcome for intelligent life, as a third hand or leg may be more of a nuisance than an advantage.
That is only half the argument though. There are quite a few other proponents on the other side of the fence. They state that there is almost no way that humanoid creatures exist in the universe. One scientist even states that if you basically started with the same stuff here on Earth that you would end up with something totally different from humans, if you let everything play out again. I kind of agree with this idea, as I think there was an extraordinary set of circumstances that led to our being so the odds that those steps would be repeated is infinitesimal. With that being said I do not think it is impossible, just highly improbable.
It is near impossible to say what is out there or whether it will look like us in some way. I would imagine that both of these arguments would hold to be true, especially if the universe is as infinite as we think it is. So that opens the door to almost every idea imaginable and all sorts of creatures humanoid and something completely different.