In "Star Trek", the explanation is given that a primordial humanoid civilization, the Ancient humanoids, seeded the Milky Way Galaxy with genetically-engineered cells to guide the evolution of life on a multitude of worlds toward a humanoid form. In the television series "Stargate SG-1", the Jaffa are explained as being an hundred-thousand year offshoot of humanity bred by the Goa'uld to suit their purposes, hence their almost-human appearance and physiology, while many other "alien" characters are actually the descendants of human-slaves who were removed from Earth by the Goa'uld. Any humans isolated on multiple planets after 100k+ years of adaptations would most certainly seem "alien" to Earthlings. Similarly, in its spin-off show "Stargate Atlantis", the explanation offered for the humanoid appearance of the Wraith is that the Wraith evolved from a parasite which incorporated human DNA into its own genome after feeding on humans, giving the Wraith their present form.