Humans have evolved over two million years, and in the span of such long history they adapted to being in the air after an unknown phenomenon changed their biological makeup, a side effect of such prompting the evolutionary chain to develop wings, a defense mechanism to avoid land predators when their numbers threatened to dive, and by the late sixteenth century humans were born with fully developed wings that belonged more on birds than on people. In modern science, Senkū feels that it's more fantasy than fact, a very unscientific thing to believe humans originally evolved from apes and then suddenly grew parts only an avian would possess? Simply illogical. Unfortunately, waking in the Stone World finds himself helpless when he can't fly.