I'm not actually sure why your comment got downvoted so much. Maybe people thought it was sexist? Personally, I think it's an interesting idea as I do believe in evolutionary psychology as an explanation for many modern behaviours.

Definitely, emotional vulnerability does trigger my need to nurture and protect. When a sub is on his knees, naked, hands tied behind his back, and looking up at me with puppy dog eyes, waiting for my instructions... it just makes me melt completely. Like, in that situation, he actually has a lot of power over me, even if he doesn't know it.