Why don't I care about people more?

Okay so here's the thing same with me.. I only car about animals I don't care if ppl die I don't care about relationships really. I have like no heart..except for animals. But the thing is when I was little like 4 or 5(which is when the brain develops the most) my dad left there was a lot of fighting also.. first all three of my brothers went to life with their mom and then my dad left to go who knows where. So I live with my momma but she told me that because of what happened I have commitment issues and just make my self not care so I don't get hurt. I put up a wall. I don't know your situation but maybe you had something tramatic or even simple to make you "put a wall up" when you were developing as a child or even something that happened recently that will eventually fade. Hope I helped?