As we know human originate from Africa, then a group of them settled in the west where we call it "Europe" and these group have similarities with each other like having blond hair, blue eyes and generally taller in hight, and we have been told that this is because of evolution and environment, that westerns (specifically northern European) have blue eyes and blond hair, and those who did not leave the Africa have dark skin and hair, which is because of hot and tropical climate and environment of the continent that make their body produce more melanin for protection,
what about Asian? including me as I have Mongol roots in my DNA, why Asian are the way they are? I mean physically, the body structure, for example they are shorter, have tiny eyes, is it the environment that affected their evolution?
Anyway, the ancestors of modern Northeast Asians (Northern Chinese, Koreans, Mongols, Japanese etc.) were Siberians who trekked across the Siberian wastes hunting elk, mammoth and other large game. Incidentally, a branch of this group trekked across the Siberian Strait and populated the Americas.
These hunter bands were very small, usually less than 50 people. So within such a small group, under such extreme environmental conditions, evolution happens very quickly and very dramatically. This is how the "squinty eyes" evolved. Those with large, round eyes fell to snow blindness and didn't live to have kids. It was as simple as that. Even today, Eskimos use devices like this to protect their eyes from the snow glare: