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Comment by cephaslr | Hacker News Reader

Correct, its a big benefit over the furry prey. Especially when chasing the animal in the hottest part of the day for hours, pre-modern people had quite a different life.

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> pre-modern people had quite a different life

You know I've thought about this, and if you look at it a certain way, I think you can say life is no different.

We still wake up as a group. We still "hunt" except the payoff is money convertible to food. We still eat together. We still sleep together (just across from one another in houses).

It's neat to think about.

Also, the massive impact of having a complex enough brain to form complex and intricate social structures made it possible for humans to dominate the food chain.

Is that right? As a beardy guy, I find beard is cooler in Summer and warmer in Winter. I'd speculate that hair allows more heat transfer to sweat. Hair also send to keep a local air layer near the skin which helps Summer-cooling and Winter-heating.

How hot and/or humid is your summer?

I don't know really, UK, so not hottest, a bit humid on occasions.

Ok I think you might have issues with actual cooling needs up above 32/35+.

But, I don't think it matters much. It doesn't help, but it's a small surface area.

Keeping a "local air layer" near your skin is not going to help at all with summer cooling. You need constant sweat evaporation to cool off. I don't think a beard is going to have much effect either way, since it's small, and our cheeks and chins are not designed to radiate heat or even sweat much compared to most of the body.

Surely if the evaporation can cool the skin surface, then a local insulation layer would prevent ambient air from heating the skin. Just as a locally warmed layer prevents ambient air from cooling the skin during Winter.

It's certainly a hypothesis I've long held but never had chance to test.

Citations for support/contradiction welcome, thanks.

Unless it's above body temperature, the local ambient air isn't heating your skin up, and if it's that hot you need to sweat profusely to avoid hyperthermia.

I think the beard is cooler in summer because you lose so much moisture from exhaling, it would go to waste not evaporating from your beard. In the winter, it solidifies and adds an extra layer of insulation. But if we were pushing that much moisture out everywhere, we'd probably dehydrate much too quickly.

It probably also explains afro style hair - keeps the heat of the sun off at midday while the prey doesn't have that.

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