@dustbird and
@UnvalidUserName I agree in principle that keeping it mysterious would've been better, but it's never been the author's intention. As early as the conversation between Jeongtae and Min-ho in the diner there was news of genetic engineering of humans playing in the background and it was clear by then where this was going.
As someone who's been genetically engineering microorganisms since the turn of the century… I just suspend my disbelief. If the author doesn't show from the beginning they intend to use hard sci-fi techniques, sci-fi is for me basically the same as fantasy. "Every sufficiently advanced technology is indistinguishable from magic" and all that.