Does melanin emit energy/radiation effectively?

Great Debates
1

" Do black people get hotter in the sun?" is a question that gets asked a lot on the internet, but its actually a good question.

We know that dark objects absorb more visible light, and possibly light in other spectrum too, and thus they become warmer in the sunlight. IIRC, Basically, photons from light excite the electrons of an object, and make it warmer.
Objects that reflect light appear white or shiny.
Objects that are good absorbers of light energy are also good emitters of light energy.

If you notice, thermal bottles are shiny in the inside, so they can reflect the energy that the warm liquid is putting out back into the liquid instead of letting the heat energy escape. I also notice that some expensive thermal coats have shiny inner lining that does the same thing. So, these materials are probably reflecting not just visible light but also infared light.

Now, lets get back to the question at hand. Since melanin is known to absorb UV light, does that mean it is radiating that energy out as infrared?
Maybe melanin also absorbs other spectrums of light that we don’t see like infrared, microwave, and radio-waves.

Maybe it radiates heat away from the body, and can actually cool someone down. To me this sounds plausible because even people that live in the densely forested areas of Africa are still just as dark as those that live in open Savannahs.

On the other hand, if melanin is both an absorber and emitter of heat energy, then that would mean in places where the outside temperature is hotter than your body temperature, then too much melanin could make your overheat.
Notice how the native people of the deserts of botswana are lighter than those of other parts of Africa.

In the Kalahari desert, and many other deserts, it can get over 110 F. The human body temperature is around 98.6 F. It seems that people in hot desert climates generally aren’t that dark.

Some of you might say a desert doesn’t have as much uv light becaue deserts are usualy not found on the equator. That may not be true. In a desert the ground is made of rock and sand; that tends to reflect uv light back up.
In a jungle or even a grassy savannah, there’s grass and dark soil that can absorb some of this uv light. In a desert you often get clear and cloudless days, but in a wetter climate, you have clouds to block at least some of the Uv light. I think you’re more likely to get sunburnt in a desert.

2

My response given here.

3

Simple answer: NO.

Unless the surface is hot enough to be radiating visible light, its color in visible light has nothing to do with its ability to radiate heat. What matters is emissivity, i.e. its “color” in the infrared. Most surfaces have fairly high emissivity. Shiny bare metal is about the only common object with low emissivity. (And it’s not as common as you’d think - most shiny metals are actually coated or oxidized, which greatly increases its emissivity. Aluminum, for example, becomes oxidized immediately after it’s cut or polished.)

And on top of that, radiation is not a major cooling mechanism for the human body. Convection and evaporation are far more significant.

4

If I understand the question, people evolved black skin because we as a species lost our hair cover, and high levels of melanin protect against UV damage to folates and to DNA. (Cite.)

If the human species originated in Africa, originally everyone had black skin. As humans migrated north, they evolved lighter skin so as to absorb more sunlight and thus be able to manufacture vitamin D.

As scr4 mentions, radiation isn’t a major part of temperature regulation in humans.

Regards,
Shodan

5

The body loses 65% of its heat through radiation. Conduction (such as heat loss from sleeping on the cold ground). Heat is lost in air temperatures lower than 68°F (20°C).Nov 20, 2015 - WebMD

6

It’s a mistake to think the current Kalahari inhabitants evolved their skin colour in situ. Their temperate-dwelling Khoe-khoen relatives had the same skintone, as doubtless did their ancestors.

7

Not just the kalahari, look at other deserts too.

Notice they also have much less eumelanin than the native people of sub-saharan Africa and Papua New Guinea despite an enviroment that is high in uv radiation.

8

Hmmm… I read the thread title as “Does **Melania **emit energy/radiation effectively?” Checked in to find out the answer.

Might be time to see about that cataract surgery.

9

Really? You sure? Truly? Other deserts too?

It’s absurd on the face of it to post pictures of people from one of the most racially mixed areas on the planet and act as if that meant *anything *about evolution of any trait.

10

Humans all have more or less the same (narrow) temperature tolerance, so no, by definition, people with darker skin don’t get “hotter” than anyone else, if they did they wouldn’t be able to survive.

Heat absorption reflects absorption at lots of different wavelengths: the visible spectrum is only a small band of the total spectrum. A white painted surface reflects most radiation in the visible spectrum, but it can still absorb a lot of radiation longer than 700 nm or shorter than 400 nm, which is why (for example) a white painted pavement or a white painted car can get quite hot on a sunny day.

Humans also have lots of other ways of regulating their body temperature (changes in metabolic rate, evaporation through sweating, changing amounts of body fat) that don’t involve skin colour or absorption of light.