I’d like to just state some of the biggest factors in controlling overall appearance traits in groups of people. The biggest is geographical location on the planet. A second is how much interracial mixing is happening, not all places are doing it, and it sounds like you didn’t think of that when you asked the question that lacked a specified region or people. A group of people who live in relatively sunless areas will slowly become pale, while those who live in hotter sunnier regions will slowly darken. The skin adapts to heat and sunlight by producing melanin, which protects the skin from ultraviolet radiation damage. This is why people of the earth are the various colors of skin that they are.
In a place like the United States, we have a lot of ‘melting pot’ going on, with constant mixing of ethnicities, so how people look will continue to slowly morph back and forth as long there are ‘pure’ ethnics producing offspring with ‘pure’ ethnics of different ethnic background. If everyone in the U.S. kept doing this, and we had no new immigrants further altering it one way or another, all people in the U.S. would slowly start to appear similar in a way I imagine Andrei Dumitriu’s picture looked. The more caramel colored skin with a hair color that is basically brown, and whose texture is between that of Caucasian and African thickness and amount of curl. Not all countries exist in a geographical area that supports a wide range of appearances, however, and not all countries have cultures that are as open to ethnic mixing either. Some countries will pretty much always be the same because they have a very strong sense of maintaining racial purity, and going hand in hand with that premise, are usually the most xenophobic countries.
People living in areas close to the equator, and areas that are constantly snowy/icy will be eternally hot, and eternally sunny respectively (from sunlight reflecting off of the ice/snow), and so people inhabiting those places will, ever so slowly, evolve to have darker skin, being more exposed to UV rays.
We will always be able to rely on the cloudy/foggy UK to produce us our cute pale red heads and blondes, though, if that’s what you’re scared of.
