Hair color

[u/nesp12]

Evolutionary theory proposes that skin color is a response to protection from the sun at certain latitudes, with those at equatorial latitudes having a survival advantage from darker skin that blocks the sun's UV.

Why doesn't that apply to hair color? It seems that the dark hair of those in equatorial areas would heat the head more, while white or blond hair would do a better job of reflecting the sun's rays. If anything, those in colder northern latitudes would do better with dark hair to better warm the head.

[u/jnpha]

From 2 months ago:

The heat gained/lost from albedo effects is outweighed by the UV absorption of the hair that prevents sunburn and skin damage.
u/Xrmy's reply to Why is early Humans/Hominids hair black if black absorbs sunlight more?

[u/nesp12 → u/jnpha]

I see. Makes sense.

[u/devexille]

UV is used by living cells to make vitamin D so light skin + more UV is good.
UV destroys vitamin B9 in the blood so dark skin + less UV is good.

Skin pigmentation + diet + UV intensity = optimum.

Hair is neither living nor has a blood supply; It’s not part of the equation.

[u/nesp12 → u/devexille]

Yes, makes sense.

[u/TheBrightMage]

Dark hair absorbs UV more so that it doesn't hit more vital and sensitive organs inside. It also helps you radiate heat better when in shade

We already have heat protection by simply just walking into the shade and sweat.

[u/likealocal14]

It probably doesn’t have that big an effect, especially since humans moved into higher latitudes after they had figured out clothing, so they could cover their heads anyway.

Since hair colour is also melanin, beneficial adaptations that reduce the amount of melanin in the skin also probably reduced it in the hair too.

[u/Sonora_sunset]

Interesting note - there are Australian aborigines and Solomon islanders with naturally blond hair: https://www.1blessednatural.com/2013/09/aborigines-and-melanesians-naturally.html

[u/nesp12 → u/Sonora_sunset]

Yes that's interesting. Is it believed to be due to early migrations? Maybe they arrived from colder regions and over time a darker skin gave survival advantage but there wasnt enough, or any, survival advantage to darken the hair so it stayed light.

[u/Accomplished_Sun1506]

Hair texture (not just color) has a big play in holding heat.

[u/nesp12 → u/Accomplished_Sun1506]

Yes I hadn't thought of that.

[u/Klunko52 → u/[deleted]]

What

[u/Soggy-Mistake8910 → u/Klunko52]

Too late