It was a beautiful day – blue sky, sun shining – but I wasn’t fooled. It was Melbourne in the Spring, and I knew there would be an icy breeze. I put on a jumper, coat and scarf, and headed out to meet a friend. When I reached the cafe, I saw her basking in the sunlight, wearing only a T-shirt. Huh? “Aren’t you freezing?” “No,” she replied smugly, eyeing my woollen layers. “I’m black, I absorb more heat than you.” Huh? That can’t be right.
Do black people really absorb more heat than whites?
Pop this question into Google, and you’ll be insulted. But, aside from responders wincing at the derogatory descriptions of “black and white” skin tones, it’s a reasonable question. After all, when you wear a black coat or sit in a black car you get hotter than doing the same activity in white. So why would skin be any different? Well, unsurprisingly, it’s complicated.
Oft sited – amongst grandfathers and milk-bar ladies – as evidence that darker skin absorbs more light and therefore heat, than lighter skin is this anecdote: In places with hotter climates, such as Nigeria, you see darker skin compared to people from colder climates, such as the pale Britons. But, if darker skin did absorb more heat, wouldn’t it be better to have dark skin in Britain, so your skin could grasp what tiny light is left? Hm.
What makes skin darker?
Human skin colour is largely determined by a pigment called melanin, which is made by tiny melanin factories called melanosomes, that sit inside skin cells – called melanocytes. Melansomes make more melanin when they are larger and not clumped together. And overall, the more melanin they produce, the darker the skin.
But other pigments also affect skin colour – such as carotene, which makes our skin orange coloured. And hemoglobin, which transports oxygen throughout the body, can turn our skin reddish or blueish depending on whether there is oxygen in our blood.
How does skin absorb light?
Light moves in waves, which can be short and powerful, like X-rays, or long waves, such as microwaves. Today, we aren’t too concerned with just any light waves – we want the ones that make us feel hot, and these are infrared lightwaves. According to NASA, they are about the size of a pin head. And when they reach our skin, or the pavement or just about anything, they get absorbed – and the energy from the light is transformed into heat.
In general, darker objects absorb more infrared light than lighter objects, and become hotter because they are transforming more light into heat.
Does darker pigmented skin absorb more light than whiter skin?
According to anthropologist Nina Jablonski, “there is essentially no difference in absorption of infrared light between dark and light skin” (Annu. Rev. Anthropol. 2004: 33:585-623). Funny thing is – I’m not sure I believe her. The two papers she cited didn’t directly measure the amount of infrared light being absorbed on the skin (which these days can be measured using an instrument called a reflectance spetrophotometry). And from first principles I can’t see why darker pigments would be any different to darker coats or cars – in terms of the light wave absorption.
Perhaps, what Jablonski meant to say, is that if there is a difference in the light being absorbed in the skin, it’s not directly translating into extra body heat. Humans of all shades and sizes have the same core body temperature – 37 degrees Celsius. Through exercise and seasonal changes, this body temperature doesn’t change because humans can release heat by increasing blood flow and sweating. Studies have shown that the heart rate and sweat rate of African Americans and Europeans, matched for height and weight, is the same when they exercise. So if darker skin is absorbing more heat where is it going?
Possibly into the melanocytes. There is anecdotal evidence, along with medical records from the Korean War that darker individuals, with heavily pigmented skin, are more susceptible to frostbite than lighter individuals. Animal studies show that melanocytes are killed by freezing than other skin cells. So, it’s possible that while more light is being absorbed, the larger melanocytes are somehow using the heat, so it’s not getting transferred to the rest of the body – but this is a lot of speculation on my behalf.
So, darker skin might absorb more light waves than light skin– we don’t really know, but going from first principles, they probably do. However, this doesn’t mean these lucky individuals are hotter in the sun because the energy from absorbed the light waves isn’t converting into body heat. Where it is going – I’m not sure. But it does seem that this is no black and white issue.
If it’s not about heat, why is some skin darker than others?
There is a strong link between pigmentation and locations that receive high doses of UV radiation. The more UV radiation hitting an area, the darker the skin.
UV radiation – which is another form of light wave, that is shorter and more powerful than infrared – can penetrate the skin, causing sunburn, DNA damage, and skin cancer. Melanin acts as a natural barrier to UV radiation by absorbing the UV radiation, but then very effectively scatters them – so they don’t harm the DNA of skin cells below. Some academics believe that darker skin naturally confers a sun protection factor (SPF) of 10 – 15.
And why bother with whiter skin then?
It’s still up for debate. The most popular reason for why lighter skin is that it allows Vitamin D production. Vitamin D is needed to absorb calcium absorption and a deficiency can lead to weak bones and impaired locomotion. The production of this handy vitamin is triggered by UVB radiation. So, when people live in areas that have low doses of UV radiation, the last thing they need is melanin scattering it.
Possibly a factor is also that color causes not just absorption differences but also emission differences. Black bodies emit radiated heat much faster than white bodies. So if you are in the tropics with darker skin, you may heat up faster in the sun, but you may also cool off faster in the shade. In the much colder climates, there is not much sun to help, so in general the key issue is how your body responds when there is little sunlight. The heat of objects with white coverings are conserved better than with dark coverings, as the dark ones will emit more “black body radiation”. So white skin may help conserve warmth. This effect could explain your Korean war data where darker skin encountered more frostbite. Black body radiation frequencies can travel right through typical clothing, so it would seem to matter what the skin color was beneath the clothing, where the heat was trying to be conserved.
This is interesting because it may further help to explain white skin, which is so disadvantageous in full sunlight.
http://stewartsynopsis.com/black_skin_is_the_genetic_parent.htm This man claims that black skin is able to survive in the cold and hot better, i don’t know what kind of education he has, but if you ask me i think he’s a racist lunatic, interesting point with the polar bear but he fails to show any form of scientific proof. I asked my self do animals have these melanocytes, and if they do why is the polar bear’s skin black, it’s fur is white though.
I am doing a study on patients with end stage renal disease and my hypothese is people with more melanin in the skin are more supcetable to kidney disease. Just a thought
Very nice article. Last comment aside. Thanks or putting alot of deep thought into it. And the first commenter made good points. I would love to see a scientific study on this. It is actually a very important thing to understand. Though many probably would not think so. Thanks for the great article.
@Surfant Good piece, I think that’s right. The advantages of dark skin is really related to temperament in the individuals, related to survival and also due the fact that infrared waves are smaller than Ultra Violet radiation.
Basically black bodies in the skies, mainly the one which will gain total attention of the science for the rest of the years, are the black holes, SuperMassive Black Holes (Galatic cores), and how it works in its nature.
Darker melanin tends to react similar to black bodies. Black bodies tends to absorv more light and dissipate it as heat than white bodies and this is unquestionable.
I’ve worked with some cirurgies in dermatologic treatments where light waves, especially hub laser, etc are used. In particular treatments and laser hair removal, patients complained about the amount of heat generated among the sessions. At first, the diagnostic seemed similar to those with white or pale skin, but the result is totally different and in some cases the upper and directly lower layers were damaged by the excess of heat non dissepation. Therefore I’ve no doubt about the Ultra Violet from the Sun and darker pigmentation being directly related.
i like your answer its the best I’ve seen so far
Black skin is far more advanced that white peoples skin. I dont want to go into much detail because i cant be bothered to educate you clowns. But the black skin is able to take extremely high temperatures and still have no damage. Whereas the white un-melinated skin cannot produce enough melanin to protect the skin and begins to chemically react with the sun. For example sun burn etc. Basically….If your white…Dont stay in the sun too long…it was not made for you. But if you persist! wear sun screen.
Studies and hypotheses aside, I am pretty dark skinned and my fiancé is fair skinned (caucaisan). When we are both in the tropics in the sun after less than a minute I feel like my skin is on fire and start seeking out shade whereas he is as cool as a cucumber basking in the sun. Whatever the science behind it is, there is no doubt in my mind that dark skin either absorbs more waves, converts them to more heat than light skin, or retain more of the heat.
Hi,
I believe she is a reptilian and as such can’t sweat and skin cracks, its true black absorbs heat and light- greedy arent they !
White colours reflect heat back into the body at night, whereas black gives off heat and loses body heat quicker, hence why we lived in caves and work at night and sleep during day when hot.
I like to share and be seen.
You also see my pupils dilate and skin flush.
Melanin is also a poison responsible for nightblindness (as brown is a longer wavelength than blue) this makes a stunting in the hypothalamus, which is why they used to head bind in some tribes to make more aggressive and fearsome warriors with little or no pain or compassion, the cabin fever effect is more exaggerated and also this is why they suffer from S.A.D. (seasonally adjusted disorder) making them lethargic and depressed which builds up into anger issues, this has a knock on effect to us and we pay the price for this misjudgement of location or failure to cleanse and eat correctly and protect from the sunlight, we needed spacesuits to land on the moon ^^, and sunglasses are lighter and easier to make than night vision goggles
We did not come from apes
Discuss why the ape cant float – yet all other mammals can and why the Gorilla has cannines.
(All babies have blue eyes when born, then the melanin poisons their body as their past sins erupt from their lack of cleansing and vitamin deficiency) Peace
some aboriginals have blonde hair ^^
They are precious people and need protection from outsiders of the same skin colouration
dude, you sound like a racist idiot, all talking about how blond haired aboriginals need protection and blacks with lack of cleansing, etc. the article on this page was fascinating, but then I read your retarded post and now feel like my IQ just lost 20 points; god help us all.