In the last episode of Shin Sekai Yori (From the New World), the antagonist Squeara faces a public trial for his crimes against the psy-powered humans. Squeara is a Monster Rat, a race of creatures created hundreds of years ago after splicing the human genome with naked mole rats. The public, unaware of these human origins, laughs when Squeara shouts that the Monster Rats are humans too, who deserve equal standing among the psy-humans they once considered gods. It is unclear whether or not Squeara knew the truth about the Monster Rats, but his punishment for attempting to annihilate his oppressors begs the question, "What is it that keeps our fragile understanding of 'humanity' together?"
The dilemma of the Monster Rats is echoed on myriad occasions throughout human history in the forms of slavery and genocide. Slavery extends the compulsion to own non-humans (objects, animals, nature) into the human realm, and genocide is the extermination of other beings based on differences. Slavery and genocide often occur simultaneously: for what reason would one capture another person if not because of a perceived inferiority stemming from their differences? Somewhere along the convoluted road of logical processes, these differences end up marking those who are inferior as being less, worthy of manipulation and ownership just like inanimate objects and tools. Ay, there's the rub - what value is there in a slave other than being a means to an end? And if these objects don't have much intrinsic worth to begin with, or cease being useful after some time, they are disposed of. Indeed, humans are the world's original renewable resource.
The question still remains: what is it that keeps our fragile understanding of 'humanity' together? It is easy to call other beings "inhumane" or "objects" or "animals" or "non-humans," but when the time comes to definitely point to what humans are, we find ourselves in a rut. Most would call the actions of Adolph Hitler and the Nazis "inhumane," but they were flesh and blood humans like the rest of us. The same can be said of the Spanish conquistadors who came to America and ravaged the natives and raped the women and children. The same can be said of the Europeans who engaged in Triangular Trade and abducted Africans from their native lands. Even before invaders arrived, American and African natives engaged in warfare among their respective tribes and sold each other into slavery. The notion of "humanity" must necessarily encompass both an embodied and an ideological metaphysical nature, because otherwise, every "inhumane" act is justified by nature of humans doing the acting. These acts are, existentially speaking, "human."
There's a certain irony in the idea that, while nowadays the academic world trends towards notions of interspecies solidarity and being in harmony with the natural world, humanity has never been able to obtain solidarity within its own kind. We've been at war with ourselves since before the idea of eugenics or the understanding of the human genome, and we're still at war even after realizing racism is based entirely on appearances and culture, with little to no genetic reflection of a "white," "black," "hispanic" or "asian" race to speak of. If such a day ever comes when people can see themselves as being equal to all other people, will we still call ourselves human? Would it even matter if the psy-humans knew the truth about the Monster Rats? Or would Squeara still have been killed, justifying everything he fought for?