Why are guys so protective of their girlfriends?

Anonymous
My boyfriend and I were walking past a homeless man who appeared a little drunk the other morning. When my boyfriend realised we actually needed to pass by the man, he grabbed me by the arm out of nowhere and moved me so that I was on the other side of him, and my boyfriend was between me and the homeless man. I got zero vibe this man was a threat to us, yet my boyfriend always gets quite protective like this. Just want to know why.
Why are guys so protective of their girlfriends?
170 Opinion