My opinion is that mate-guarding among humans is more common than not. In fact, it's sort of socially accepted... QUITE socially accepted. Guys who don't mate-guard are usually looked upon kind of strangely.
Remember a time when I was at a bar with a chick (call her "X") I was dating and was talking with her friend. "X" was over talking with some other dude who was better looking, taller, more built than I. The friend pointed it out to me and I shrugged and tried to go back to the conversation she and I were having.
She said, "Aren't you going over to pull her away from that guy?" I shrugged again, played dumb and said, "Why would I do that?" knowing full well why most guys would do that. She seemed exasperated and later "X" told me that the friend had complained that I mustn't care for her all that much if I wasn't threatened by other men talking with her.
Kind of interesting.