system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What's the reason behind asian people's eye shape?
gpt
There is no complete evolutionary explanation for the apparent slant of the eyes common to Asians. The configuration results from a fold of skin of the upper eyelid, the epicanthic fold, which tends to cover the inner corner of the eye.

Dr. Frank Poirier, a physical anthropologist at Ohio State University, says the classical explanation of epicanthic fold depicts it as an adaptation to the tropical and arctic regions where many Asians live. The fold is described as a sun visor protecting the eyes from overexposure to ultraviolet radiation or as a blanket insulating them from the cold.

According to Poirier, the problem with this theory is that a substantial portion of the Asian population evolved in areas outside of the tropical and arctic regions. In addition, he says epicanthic fold is not limited to Asians. ''John F. Kennedy had a variance of the fold and it is found among Europeans, especially the Irish,'' he said. ''It`s just less prevalent.'' The fold is also found among infants worldwide. Poirier attributes the fold to pleiotropic genes--single genes that control more than one characteristic or function--but he has no explanation for its origin.