In the world of the Fifth Season orogenes are about as close to wizards and witches as you can get. Popular culture might also liken them to the earth benders of the Avater: The Last Airbender television series. Although there’s no explanation for where the power to move tons of rock with your mind comes from, there’s a small detail that Jemisin inserted into the world she built. In fact, it was inserted into the base of the neck in the form of a sesspinae. This addition of an alternate biology adds a way of explaining that isn’t complete but comforts a reader. Wizards, warlocks, witches and the like all classify as fantasy which is really only tangential to science fiction. Making the inhabitants of the Stillness in possession of an organ that interprets waves of energy is one of the things that Jemisin does to depart from fantasy. Paired with her desires to keep her science fiction as closely based to real science as possible, I think that having something to move from like the sesspinae is important. The counter to orogenes, Guardians, also can explain their abilities by pointing to the implant they received when they were children.
I think that the ability for characters to explain what they do lies in the philosophical base of science. Science seeks to understand phenomena and therefore, a science fiction novel written by an author aware of the failures of science fiction of the past needs to have ways of explaining even the more mystical elements in the book. If Jemisin had gone the other way and flat-out written a fantasy novel there wouldn’t be a way of adding in her commentary on modern social issues. That genre relies on gods and ancient sources of power that require dogmatic loyalty. That loyalty is to a being that is not human, yet it dictates human life. Therefore, Jemisin has accomplished a good example of humanistic writing though the people that populate her stories may have a little more than the rest of our bodies.