The humans, for a stronger generation, crossed their genes with animal ones, thus making a new breed that has a thirty genre (omegas, alfas, and betas). The omegas "repay" society (leveling the balance of the world) by "giving away" his offsprings (they still have contact with them, but they are "given" to be happy in other couples lives too.
I liked the story, very fluffy, with the unexpected "forced adoption" that, all in all, was not so hard to sympathize with, considering the way the author smartly prepared us beforehand.
Omega Shunki