As for the different facial traits in different parts of the world, they are due to adaptations to the local environment, genetic drift (changes due purely to chance) and perhaps also due to sexual selection (e.g. different cultures tend to have different standards for beauty). For example, wiry hair is adaptive in hot climates because it allows air to rush in to cool the head while also trapping air to insulate the head against the sun. Straight hair also protects the head from the sun, but air circulation is poorer, which tends to conserve heat in cold weather, but in hot weather, it is harder to cool the head. Therefore straight hair probably evolved in cold climates. Another example is the rotund torso and shorter limbs of cold-adapted Europeans compared to Africans, who tend to be more slender and have longer limbs. The longer the limbs and the more slender the torso are, the more surface area they have and therefore the more body heat they dissipate to the environment. Neanderthals, who are even more cold-adapted than the Europeans, have even more rotund torsos and short limbs. Finally, East Asians tend to have flatter faces and wider foreheads because they retain juvenile head-to body proportions as adults, which is a quick and easy way to enlarge the brain. Humans in general use the same trick, known as neoteny, to evolve large brains than our ape ancestors. Therefore we look like juvenile apes more than adult apes, since juvenile apes have larger brain to body size ratios than the adults.
