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I'm trying to determine whether my skin and hair colors are consistent with the climate of my planet, if I've done them correctly, within reason.

Skin colors

Hair lightness

Hair redness

Climates

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    $\begingroup$ Minor note - in humans, red hair and green eyes are due to recent mutations and there's no evidence of natural selection. Your distribution would require either convergent evolution (totally possible; happened in humans with at least lactose tolerance , high alt adaptatiin, and malaria reistance ) or immigration (also totally possible) $\endgroup$
    – N Brouwer
    Apr 12 at 23:09
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    $\begingroup$ Blond hair also naturally occurs in some populations of people with black skins. med.stanford.edu/news/all-news/2012/05/… $\endgroup$
    – DrBob
    Apr 13 at 14:40
  • $\begingroup$ Was expecting blue people with purple hair. Effect of Climate on Hair and Skin Color? (Those aren't 'your's, those are them; the regular ones) $\endgroup$
    – Mazura
    Apr 13 at 17:39

2 Answers 2

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Migration happens

Great effort, good to see a well-researched question with easily read visuals. Unfortunately, migration patterns tend to throw a spanner in the works, since people typically migrate faster than the skin pigmentation of their population evolves to compensate. Look at Australia - prior to the arrival of Europeans there were broadly similar skin and hair tones all the way from the northern tip of the country down to Tasmania. The maps you have seem plausible to me if and only if there has been no significant migration of people for tens of thousands of years.

My knowledge of the subject is not much deeper than having read Guns, Germs and Steel, but I'm not sure that there is any period in the real world in which things were stable for so long that everyone stayed in their little corner of the world long enough to standardise pigmentation by latitude and climate. (It would require that there are no natural disasters, no major advances, no significant conflicts, no climate changes...)

That said, using it as the basis of determining the skin and pigmentation of the different populations in your world is fine, no one is going to find it jarring. (Whether it is desirable to spend lots of time describing everyone's skin and hair colour is another matter, given sensitivities around the subject.) However, if you want to take the next step then work out a few major changes that have occurred in the last five to ten thousand years that have caused major migrations - land bridges between continents appearing or disappearing, volcanic eruption driving people away etc - and throw in some migration events that will change it up a bit.

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  • $\begingroup$ You make great points about migration. The accuracy of the map will depend on how common migration is. Up until the last 300 years skin pigmentation was predicted very accurately by lattitude, modified by factors like habitat, altitude and diet as pointed out by others. Skin pigmentation tends to evolve fairly quickly With lat. Patterns recapitulating across all of the America's in both N and S hemispheres in the last 20k years. It's also resistant to migration, which has been common in eg Africa and India for 1000s to 10,000s of years yet patterns persist. $\endgroup$
    – N Brouwer
    Apr 12 at 22:56
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Assuming the planet shown is simply another version of the Earth, Then skin and hair colours would not necessarily be darkest around the equator, but in places with a combination of maximum sunlight and minimal moisture.

Hot and HUMID places tend to create rain-forests, and you do not need particularly dark pigmentation under the shade of the canopy. The darkest skin and hair with the most pigment are needed when humans live on a savannah or a desert, where there is little way to hide from the oppressing UV light.

Therefore, I would adjust the map, and move the darkest combo to the deep inland part of the central continent ( The Red and Yellow climate parts: This is going to be your Sahara and/or African savannah), and keep the coastal and island regions lighter hued.

This is also going to influence your population levels. If you insists on matching coloration with environment, and not allow much migration, then the lightest and darkest colors will be severely under-represented, because these tend to evolve in the harshest environment.

With the map as-is, you are likely to have only about 3% "white" people, and maybe 10% "black" people, because you placed them in places not really contingent with population increases (jungles that cannot be tamed without massive, industrialized effort, or various types of desert).

Aside from that, your population and proliferation of redheads is orders of magnitude too big, unless red-hair colour works different in your reality. IRL, every possible genetic combination that leads to red hair is recessive, so there is almost no way for Redheads to be that numerous, unless they practiced complete genetic isolation for tens of thousands of years, and also bred like proverbial rabbits.

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  • $\begingroup$ Good points about rainforests. Higher elevations also experience higher UV and have darker coloration than adjacent lower areas $\endgroup$
    – N Brouwer
    Apr 12 at 22:42
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    $\begingroup$ Don't underestimate the value of sexual selection. If red hair is the "prestige" color in a culture for a thousand years or so, expect it to become common well beyond what a simple evolutionary analysis would tell you to expect. $\endgroup$
    – Mark
    Apr 12 at 22:47
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    $\begingroup$ @mark this is a good point. Sexual Selection can do wonders, and could make for an excellent cultural compnent in fiction. In humans for hair-skin-eye color, however, many of the genes are the same, so sexual selection would have to be very strong to overcome natural selection base on UV light, which is one of the strongest signals of selection in our genome after disease. That said, we still haven't figured out exactly what links UV and skin color. It's probably related to vitamin D, probably not to cancer, but still details to work out $\endgroup$
    – N Brouwer
    Apr 12 at 23:03

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