How did modern homo sapiens evolve differences?

[Nick]

We know that all humans evolved from apes and the first human races came from Africa.
My question is:

1) Why and how did people who went to Europe became blonde in skin/hair colour?

2) Why and how did people who went to China/Asia became Mongoloids
3) Why and how did people who remained in Africa became blacks?

[Shansi]

Lots and lots of pressure from the environment and society creates differences in our species.

'Race' isn't really a thing - Negroid, Mongoloid, Caucasoid are all oversimplified genetics.

Weather, living condition, amount of sunlight, diet, social preferences contributes to our different looks. Those who moved further north into colder places evolved light skin as a response to low sunlight (which helps produce vitamin D and other vitamins). However, those who moved north but maintained a rich fish diet (contains lots of vitamin D) retained a darker skin color (inuit or eskimos). Blond hair became dominant out of social preference (it's shiny = it's eye catching and at the time, it was rare).

Arabs for example are technically caucasoid (they descended from the Caucaus mountain) but have tan skin (because of sun exposure).

East Asian features such as equal fat distribution (that's why most looks thin), neoteny (retaining of youthful traits), and double eyelids all help protect the population from windy, sunny, and cold weather. Whereas eye color and hair color vary in western europe, it is fat distribution that varies in Asiatic population.

Also, Europeans brewed alcohol so their tolerance is better than the east asians who preferred boiled water and tea. Asian diet also contributes to the height difference. Skin color in asians vary a lot - northern asians are very fair while going near the equator, you'll get darker skin asians (again, due to adaptation to sunlight)

African populations are the most diverse in the world. Height distribution in Africa is like the eye color of Europeans and the fat distribution of Asians - it varies a lot. Dark skin is necesarry because of the amount of sunlight exposure - European skintone and Norther asian skin won't work very well in Africa. You'll get sunburn.

Also, northern Japanese tribes like Ainu used to nearly look like Europeans (they were hairer than the Yamato Japanese people and had light colored eyes) although they were not european but rather mongoloid.

Basically, if a population is isolated and breeds with itself = over time, you'll notice that they will start to look different from everybody else.