Did the authors take into account that humans have 'culture' (and structures of (male-dominated) power associated with it) whereas other species don't to any great extent?
> What explains the GAP? While evolutionary frameworks have traditionally been the dominant lens through which the GAP has been viewed— assuming its existence without direct empirical evidence—these theories focus exclusively on opposite-sex attraction, mate selection, and reproductive success. Within these theoretical boundaries, explaining the variation in same-sex ratings and the cultural differences in the GAP becomes challenging, suggesting that factors beyond biological predispositions also play a role. Given these limitations, sociocultural factors and norms merit further consideration. As noted earlier, female beauty is idealized in many cultures and reinforced by media, advertising, and societal expectations. Internalized beauty standards may foster unconscious biases, leading to, or amplifying, the observed difference.
But the study is mainly concerned with verifying the existence of the gap.
Btw, a lot of animal hierarchies are also male-dominated.
You could read the study to determine answers to questions like this. Instead you want somebody else to read the study and explain it to you. You should expect questions like this to be downvoted.
> Our findings confirm the existence of a robust “Gender Attractiveness Gap” (GAP), with female faces rated significantly more attractive than male faces across rater genders, cultural backgrounds, and portrayed ethnicities.