This manga have some real pointy ethical questions.
From previous chapters example, humans hunt monsters as animals and eat them.
Like with Dumbys family was hunted for thier hearts.
But some monsters are as intelligent as humans, not to mention they can communicate with us too.
Morals always take a back seat when survival is at stake, but its still a really strong 180 turn to go that far in 4 years.
If animals were able to talk to us by binding their soul to us today, animal rights groups would go apeshit over less..