Not a religion, a spirituality, or quite like any other human ideology , Otherkinity is for those of us who are something other than human. As a group those who experience Otherkinity are called: Otherkin. This unique phenomena of believing oneself to be nonhuman typically involves identifying as mythical or fantastic creatures not seen on Earth in mind or in spirit. At the core of it, It is an ontological identity phenomenon. The growing community and subculture of us who are non-human have been around for decades. Some may even believe that nonhumans may very well been part of subhuman culture for far longer than our communities recorded history. This is something that can be seen in many cultures worldwide of human/animal hybrids, such as the Egyptian depictions of human bodies with animal heads for example.
Though the term we now use today, Otherkin, was not founded until 1990 on the Elvinkind Digest(a mailing list for those who identified as Elves), we who experience non-humanity have collectively gathered around this experience long before we had a word for it. Proving this, our recorded history has us traced back to the early 1970's, yet even this is not likely where it all began.
The roots of Otherkinity vary in many ways however, which leads tracing our community back in a few different directions. The realty of it is, that the Otherkin community we know today, is a mashing of multiple non-human communities into one big conglomerate. Most non-human groups developed separate by species or other means. Groups like Draconics, Unicorns, Elves, and others; each grew around their own groups respectively. Today though, most of us non-humans gather within the Otherkin community.
The main part of this phenomenon that needs to be understood though, is that it is an integral identity at its core. Whether someone's personal belief is through spiritual means, or based in psychological reasoning, the identity is something inseparable from the individual. The second important part is that the identity is involuntary. This is what sets Otherkin apart from other groups like furries, which we are not. Otherkin do not choose to be Otherkin, they simply are. It is what they are as their true self.
Being Otherkin is a state of mind, and a state of being. Those of us who are Otherkin, can't turn our non-humanity on or off, we are always like this. Its not a show, an act, or a game. Being Otherkin is our way of life, and way of being. Going through mundane life, we are all around you. We could be your post office worker, your flight attendant, or anyone really. Wherever we are, we are still always Otherkin, even if you can't see it.