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Interesting Science About The Colour Of Human Skin

man gets inked in a tattoo parlour

If you’re buying a gift for a young artist, a favourite of mine is a box of skin tone pencils or pens.  My Crayola box of the 80s included a ‘skin’ colour — in reality no one’s skin — symbolically and problematically the crayon was ‘white skin’. An entire box of skin tones is a far more inclusive gift.

Derwent skin tone pencils

WHY THE DIVERSITY OF SKIN COLOUR?

Our hairlessness has become a source of what we think of as beauty, a reality validated in every National Enquirer article about a “wolf boy”. It also has widespread consequences for our health and quality of life. It is the reason for the origin of melanin (the compound that, when present, makes dark skin) in sunny regions. The production of melanin in cells is just under the surface of the skin evolved in Africa, along with our loss of hair. All of our ancestors produced melanin and so were dark skinned, but when some of our ancestors moved out of hot climates, melanin blocked too much sun. At least a little sun on the skin is necessary for our bodies to produce vitamin D. Dark-skinned individuals in sunless places suffered rickets. The died, and so, with time, pale-skinned genes were favored, not just once but several times independently, with the northward migrations of humans. In other words, the variety in our skin color would not exist were our skin not exposed in the first place by our lack of hair.

– Rob Dunn, from The Wild Life Of Our Bodies

 

MORE

1. Nina Jablonski on the Evolution Of Skin, a Research Unplugged Podcast, available on iTunes U podcast from Penn State. She also did a TED talk, breaking the illusion of skin colour.

NOTES FROM THE PODCAST

Human skin is not much different in its basic structure from the skin of other animals walking around. But other mammals tend to be covered in hair, so it looks quite different. Humans are functionally hairless. This makes us very sweaty.

The next uniqueness is that human skin comes in a variety of natural colours. This is unique to our species.

The last unique feature of human skin is that compared to other animals we actually do things to our skin. We decorate it and use it as a canvas for self expression. Makeup, tattoos, piercings have great social significance.

Nakedness and sweatiness go together. In the course of evolution of our lineage, skin is hard to learn about because skin cannot be preserved. Nevertheless we have good evidence and we know we’ve had naked skin for a long time. This has been necessary for us to be more efficient sweaters. Humans and other primates are excellent at losing body heat through sweat. A dog pants to lose heat. A sheep loses heat through a mechanism at the base of its brain which allows it to cool a lot of blood flowing through the brain in particular via its nose. The more active the primate the more numerous its sweat glands. We come from a type of ape that has a moderate number of sweat glands. Other apes were extremely energetic in their activity, similar to modern humans so they must have had the ability to cool themselves with sweat glands. We’ve had excellent sweat glands for 2 million years.

When a horse sweats a lot they actually lose their ability to keep cool because their hair becomes compressed and their ability to lose heat through evaporation is limited. So the more hair you lose the more cool you can become by sweating. This is why we became hairless.

The ancestral form of our lineage lived only in equatorial Africa (2 million years ago). Hairless skin without pigment is very subject to burning. Recently we’ve become very aware of the sun but before that people didn’t protect ourselves well from the sun. Before that unpigmented skin burned a lot. This damage is not just the kind that causes you to have wrinkles and have skin cancer when you’re older but is actually damaging the DNA in your body essential for normal health and reproduction. So all of a sudden sun doesn’t become a little bit bad for you but a positive liability.

It was at this time in our evolutionary history that our species became darkly pigmented. All of us around 2 million years ago were darkly pigmented. The story of skin pigmentation then really starts out at this common denominator and it becomes interesting as the population disperses. This occurred quite quickly and we have humans going into Eastern and central Asia then Europe over the next million or so years.

When people went into these places their skin colour underwent major changes. Pigment in skin not only protects against dangerous effects of ultraviolet radiation but also is to do with making Vitamin D. Evolution is happening in our skin all the time. The pigment is filtering out a certain amount of radiation but also allowing a little bit in so that you can make vitamin D. Organisms like humans are remarkable in that through the course of natural selection we’ve tinkered with the amount of pigmentation in skin exactly right.

Outside the tropics, where humans first evolved, there isn’t very much of the UV radiation that makes vitamin D, and yet we need vitamin D to be healthy. That’s why, as humans moved into higher latitudes lost pigmentation, many of us have lightly pigmented skin, especially in northern Europe and northern Asia. This pigment (melanin) can be produced temporarily by people who tan. It was an important response that evolved in some people to deal with the increased UV that occurred for part of the year. (Summer)

We use skin constantly to advertise ourselves. Even for those who put no decoration on our skins, our skin tells a lot about your state of health. It immediately gives a signal to any observer about age, how much sun exposure you’ve had and what your likely ancestry is, even from 50 yards away.

If you have a certain amount of makeup on of a particular kind, or if you have tattoos of various kinds and positions we learn even more about you before you say anything. We use these cultural mechanisms to great advantage, to give people info about ourselves before they even talk to us. In modern society where speedy social interactions are the rule rather than exception more and more people are relying on this kind of advertising. (eg black and white goths)

There’s a difference between cosmetics and something like a tattoo or piercing. Many older people can’t relate to tattoos as a visual medium and think it’s a foolish thing to do. After interviews, I realise young people think extremely carefully about it because they want a tattoo to be another symbol of themselves. Tattoos are not something people undertake frivolously. The vast majority consider it very carefully. It speaks of very deeply held aspirations about themselves, and have become extremely popular in the last 10-15 years.

We use our skin to gather information about our environment through the sense of touch. A lot of animals do this but we use our sense of touch tremendously, especially the tips of fingers and face. We gather a huge amount of info about our environment and about each other. Primates evolved to constantly touch one another. Humans living in a hunter gatherer society have a tremendous amount of physical touch between members, but our society has regulated against most of this kind of touch. If we were chimpanzees a roomful of students would be intertwined with one another, grooming. We tend to discount this part of our legacy. Touch is very important to normal childhood development and physiological well-being. Individuals in nursing homes do much better when they are touched and hugged.

2. Surprising Siblings: Black and White Brothers Are Actually Twins shows that people of Caribbean descent often carry European DNA.

3. Some Doctors Aren’t Wild About Self Tanner And Prefer You Stay Pale from Jezebel.

4. And if this article doesn’t stop you from using sun beds nothing will, from Women’s Health.

5. Based On The Colour Of One’s Skin, in which we are cautioned against confusing skin colour and racial identity, from Zero At The Bone

6. Crayons that come in lots of different ‘skin colours’.

7. The Enduring Popularity Of The Tan from The Beheld

8. A depressingly large number of Nigerian women use harmful skin bleach, from Jezebel

9. Tanning Is a Young, White, Female Problem. And It’s Deadly, also from Jezebel.

10. Pigmentation: the simplest of complex traits not so simple? from Discover

11. Neanderthals Came In All Colours, Discover

 

Header photo by Paladini Mauro

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Everyday Words Whose Scientific Meanings Are Different

THEORY

In everyday language, a theory is something that hasn’t been proven. We use it to mean ‘hypothesis’.

I don’t know why socks go missing but I have a  theory.

MARK COLVIN: Do you think that to a degree [the theory of evolution is] a communication failure by science? Do you think that just the very word, “theory”, in the “theory of evolution” has misled people?

RICHARD DAWKINS: Yes, I think that’s not the only communication failure. I think that simply not bothering to go out there and talk in the public square is part of the problem.

– from this interview.

Here’s how the word ‘theory’ works in scientific literature, compared to some similar words:

  • Hypothesis–>An educated (or uneducated) guess
  • Science Method–>The 7 step process to test said guess
  • Theory–>The “why” of something works
  • Law–>The “what” of something that works

courtesy of Freethought Blogs.

NATURAL

In common usage, ‘natural’ = ‘good’.

The Incredible Arrogance of Thinking ‘Natural’ Means ‘Good’

This one is a marketing difference and it pays to remind oneself regularly: brown packaging and ‘natural’ on the box doesn’t mean jack. Cancer. That, too, is ‘natural’.

CASUISTRY

A college professor taught me the word “casuistry” when it came up in office hours during a conversation we were having about a presentation I was slated to give on John Donne. It has two definitions: the first more technical definition has something to do with applying abstract rules to concrete instances. The second, in more common usage, is something like “specious, sophistic reasoning.” It’s especially associated with the Jesuits, who (allegedly) used it to rationalize light punishments for aristocratic sinners. It’s a great word. I especially like to use it when I’m losing an argument, because even if, say, my husband is being perfectly logical, nothing undermines a debate by calling him a casuist.

– Persephone

SYMBIOSIS

In science, symbiosis means ‘a close relationship’. There are four main kinds of symbiosis, one of which is mutualism.

In everyday English, when people talk about ‘a symbiotic relationship’ we are most often talking about mutualism, or ‘a mutual relationship’, which would be technically more accurate.

Apart from mutualism,  three other types of symbiosis are:

  1. Commensalism, in which one species benefits while the other remains unaffected
  2. Parasitism, in which one species benefits while the other is harmed
  3. Neutralism, in which both species are unaffected

TOXIN

Common Usage: Man-made chemicals

Scientific Usage: Biologically produced poisons.

(Toxoid: A toxin which has been rendered no longer toxic eg. a vaccination is ‘toxoid’, which doesn’t exactly help the vaccination cause.)

 

MYTH

Myth
from A Comprehensible Universe: The interplay of Science and Theology

EPIDEMIC

Scientists generally use the term “epidemic” to refer to a disease that occurs suddenly in a discrete population, an outbreak. An epidemic is not declared on the basis of high numbers but on the speed or rate that new cases pop up. In the nineteenth century, the word was used almost exclusively to describe a wave of infectious disease. In the typical graph of an epidemic, the number of cases is plotted against a measurement of time, such as days or weeks, to show how quickly the disease is spreading.

With the notable exception of AIDS, in modern times we’ve had less experience than previous generations with fast-moving infectious diseases, like polio or smallpox, that can affect entire populations. As a result, the time component of the definition of an epidemic has become less crucial. As one consequence, the definition of ‘epidemic’ has broadened. Now, we use the word with little reference to the speed at which new cases are occurring, which puts us one step away from the original usage. And when we talk about epidemics of conditions that are not contagious — such as skin cancer, autism, anorexia nervosa, and teen pregnancy — or conditions and situations that are not even real diseases — like alien abduction, or satanic child abuse — we’re two steps away.

— Unstrange Minds: Remapping the World of Autism by Roy Richard Grinker

Related Link

What scientists say in research papers vs. What they actually mean, from io9

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Picturebook Study: Colour Analysis

THE IDEATIONAL ROLE OF COLOUR

In its most basic role, colour is used by illustrators to represent the hue of things as we think they most often appear in the world. Despite the link to veridical reality, there is still a reliance upon archetypes. Not all cows are black and white, not by a long shot. Yet the cow as illustrated on your milk carton is probably black and white, because this is how we think of cows.

THE TEXTUAL ROLE OF COLOUR

  • The same colour might be used over and over to create a meaningful imagistic pattern, like the colour red in the film Sixth Sense (a ‘colour motif‘).
  • Colour may be used contrastively to highlight or foreground some element within a composition to make it especially salient to the viewer. Anthony Browne might use a square of light coming through a doorway to segregate one character from another, for example segregating daughter from father in Gorilla.

THE INTERPERSONAL ROLE OF COLOUR

This is about the emotional effect colour has on the viewer and refers to the visceral response we have, independent of the actual story being told. Other useful words are: ambience, mood, atmosphere.

  • A picture book filled with bright, light colours might feel childlike and joyous.
  • A picture book rendered in monochrome might make us feel melancholy or reflective or sombre.
  • Sepia tones put us in mind of an historicised story.
  • Colour and texture can be either infused or defused (I’ve also heard the term ‘diffused’ or we might say ‘drained’.)
  • Lighting effects can make a picture seem either dramatised (e.g. arte noir) or flat (by removing any aerial perspective).
  • We can speak in terms of vibrancy, which is another term for saturation (lots of colour, or tending more towards monochrome). Vibrancy creates excitement whereas muted colours create gentle, restrained feelings, or perhaps flat feelings. Note that ‘muted’ can refer to either light or dark images. Rosie’s Walk is muted but light, whereas Wolves In The Walls is muted but dark.
  • Vibrancy/saturation is tied directly to the variable of ‘value’ — the lights and darks — imagine the illustration blocked out in grey scale. That’s its value. (Illustrators often do a values sketch first, and digital illustrators often work by setting down the values and only adding colour on separate layers after all the value details have been finalised. This allows hue and vibrancy to be changed easily at any stage of the publishing process.)
  • We can speak in terms of warmth, according to how yellow/blue a picture is.
  • Warm colours and cool colours can signal the temperature of the environment but also the emotion of the characters, or both.
  • And here’s something not seen in digital art software: we can also speak in terms of ‘familiarity‘. Familiar illustrations will have more colour differentiation whereas ‘removed’ illustrations will have less. A ‘familiar’ ambience is made up of lots of ‘colour differentiation’. (Lots of different colours.) The reason it’s called ‘familiar’ is because the real world is also made up of lots of different colours, and we are familiar with the real world.
  • When illustrators make use of a reduced palette they are making the conscious decision to move readers away from the familiar and into the strange. There will be a reason for wanting to move us away from reality and it’s just a matter of working out what that reason is when analysing an illustration.
  • This removal from reality needn’t be in the literal sense — it might be figurative.
  • Vibrancy, warmth and familiarity are all simultaneously active — they don’t cancel each other out.
  • An opposite of the ‘familiar’ colour scheme might be described as ‘saudade’, from Portuguese. Saudade describes a feeling of longing, melancholy or nostalgia. (Saudade Pinterest Boards)
  • A mixture of familiar and saudade colour palettes in the same book can show the difference between, say, characters who are enjoying life and a part of their environment and those who are removed. (As an example see Anthony Browne’s Piggyback — the father is depicted in vibrant colours while the mother is removed. Another is Cooke and Oxenbury’s So Much.)
  • In picture books you often see a foreground without background setting — a part of the scene has been pulled out and placed upon a blank (often white) background. This is done to draw the reader’s attention to the emotion in the picture rather than to encourage a focus on the ambience.
  • Splashes of colour within generally dark pictures usually mean something in the story, too. For example, a bright splash of colour that runs through a book might foreshadow a happy ending.
  • Another kind of colour contrast used in picture books: A coloured frame or margin that carries the ambience. Try dividing the picture into parts according to light and dark, in shadow or in light, warm or cool, and see how the composition looks now.
  • White margins don’t mean much in picture books because they’re neutral but black margins do have an effect. We’re less inclined to react emotionally to a picture when framed in black. (Art students are told to avoid black straight out of the tube altogether, presumably for this reason.)
  • When a children’s picture book is entirely black and white the decision has been made to forego the opportunity for ambience, or at least downplay it. Even in black and white pictures you still get the full continuum between simple black and white line drawings with no ambience to drawings that include shading, hatching and dotting to create texture and then there are those that emphasise lighting effects to create a greater sense of atmosphere. (These last kind have infused ambience rather than ‘defused’. Another word for ‘defused’ is ‘flat’.)

Notes are from Reading Visual Narratives (2013) by Painter, Martin and Unsworth

FURTHER READING