Short Answer 
The epicanthic fold likely evolved in ancient Asian populations as an adaptation to protect the eyes from cold climates and harsh environmental elements, such as strong winds and dust storms. Additionally, its presence may stem from genetic variability, representing natural diversity rather than indicating any inferior traits.
1. Adaptation to Cold Climates
The epicanthic fold, a skin fold at the inner corner of the eye, may have evolved to protect against cold air. This adaptation was crucial for ancient Asian populations living in harsh, cold environments like:
- Tibetan Plateau
- Mongolia
- Siberia
By reducing air exposure, the fold helped to maintain eye comfort and function during frigid winters.
2. Protection from Environmental Elements
Another significant role of the epicanthic fold is its protective function against environmental factors. This includes shielding the eyes from:
- Strong winds
- Dust storms
- Sand in deserts
Such protection was especially vital for those inhabiting the steppes and deserts of Asia, where harsh weather conditions are common.
3. Genetic Variability and Evolutionary Byproducts
Finally, the shape of the eyes may arise from a combination of genetic variation and evolutionary changes. It’s believed that:
- The epicanthic fold might not be a direct adaptation but rather an outcome of other genetic factors.
- This trait could also simply illustrate the natural diversity found within human populations.
Understanding these factors emphasizes that eye shape reflects complex evolutionary histories rather than any inferior traits.