To summarize: It is indeed true that many metrics of beauty are socially constructed. However, it is unequivocally clear that many others are universally defined, as these constitute cues of phenotypic quality that hold true irrespective of cultural setting or time period.
I figured you would enjoy exploring the above mentioned article.
The question remains in my opinion... Which is more complicated, the human mind's ability to create complex meanings to concepts like beauty or the fluid world around us that we are constantly trying to define.
It's why I believe that the human mind is without border, we cannot fathom or place a depth to it and that's why when we discuss about distinctively unique things such as beauty, we cannot come to a total definition or a finite view. Our mind is constantly evolving and changing our perspective too as we adapt to life and learn. The subject of beauty is complicated and this is why I tried as much as possible to cover angles and areas within my experiences as well.
I however love the contest, it challenged me to thoughts and I was able to express a whole lot about what I feel towards beauty in context.