We trained chickens to react to an average human female face but not to an average male face (or vice versa). In a subsequent test, the animals showed preferences for faces consistent with human sexual preferences (obtained from university students). This suggests that human preferences arise from general properties of nervous systems, rather than from face-specific adaptations.Another study claims to explain why beautiful people are paid more.
Interestingly, employers thought beautiful people were more productive even when their only interaction was via a telephone interview. It appears that the confidence that beautiful people have in themselves comes across over the phone as well as in person.I don't think that the study tested confidence, so that is just one possible explanation. Maybe beauty is correlated with articulateness or something else.
I am not sure which seems more unlikely -- chickens detecting human beauty or employers detecting over the phone. Either way, it appears that beauty is not just some cultural prejudice.