There is also another point of view; the reason we have a concept of 'good looking' human faces to begin with is because, at some point, the human brain has to

There is also another point of view; the reason we have a concept of 'good looking' human faces to begin with is because, at some point, the human brain has to distinguish between looking at another ally (human) or a possible predator. So better looking people are just humans that look more.. human. It's not a stretch then for other animals such as chickens to also think this way, and they may get confused looking at less attractive human faces that resemble other predators that they are hard coded to run from.