we are animals but unlike other animals we were made in the image and likeness of god (intellect and will). we can choose to be like how god made us or we can choose to turn away from god towards things that aren't god. this act of turning away is what evil (sin) is.  god made us humans to have 1 partner (assuming spouse doesn't die). that's why things like telegony and pairbonding are a big deal because it's shows monogamy is true, and why cheating feels like shit.
Australia