Luke Skywalker? Han Solo? Leia Organa? They're humans... Right? Well, there are actually multiple theories about this, but they are all unreasonable in different ways. The first theory is that these english-speaking characters are complete aliens that have evolved to the advanced form of a human. This is perhaps the most unreasonable, because it is almost completely impossible to have a random species evolve identically to another species, and have these two species come from extraordinarily different environments. The second theory is that they are indeed humans, and have just traveled to the Star Wars universe. Lots of things are wrong with this theory, because it takes place a long time ago, in a galaxy far, far away, and our current technology is nowhere near capable of traveling this far of distances, and I'm pretty sure the past is not the future. Therefore, it is impossible to have humans in the Star Wars universe in real life.