There are some people on YouTube and the internet who are saying that white people are just albinos with a different degree of albinism. How can I explain to them that they are scientifically wrong?
-An undergraduate from Missouri
December 8, 2010
You're absolutely right -- different shades of skin are not just different degrees of albinism. They are more like different coat colors on a cat. Few people would argue that lighter colored cats are albinos!
In fact, albinism and merely having fair skin are, in humans, mostly due to different genes*. This certainly argues that being albino and being pale are not just different versions of the same thing.
Skin color comes from pigments called melanins. The more of these melanins you make, the darker you are.
People with albinism make no melanins. Fair skinned people make different levels of different kinds of melanins.
Just because they both involve melanin in the skin does not mean light skin is just partial albinism. Any more than being near sighted is just a less severe form of blindness.
Another big difference is that albinism is almost never a survival advantage. I can't think of any situation in humans where being an albino makes you stronger. Even albino animals are more likely to get skin cancer or go blind when compared to normal animals.
The lighter skin of some Europeans and Asians was useful though. Looking at DNA we can tell that a few thousand years ago, the DNA difference responsible for pale skin in Europeans suddenly became very common. In the blink of an eye (genetically speaking), having pale skin helped people survive.
The most likely explanation for this is the lack of sunshine and cold winters of northern Europe combined with the introduction of agriculture. These factors strongly favored pale people. And so they became common.
Like I said, nothing like this has ever happened with albinism and it probably never will. Albinism is more than pale skin. It almost always comes with very poor vision which is never an advantage. It can also have other complications like bleeding in the lungs.
So albinism and pale skin are definitely NOT different points along a spectrum. They are distinct.
What I thought I'd do for the rest of the answer is focus a bit more on the differences between albinism and fair skin. To do this, we need to take a step back and talk about melanins.
More than Just Skin Color
When most people think of melanins (if they do at all), they think of tanning which is only part of the story. Special cells called melanocytes do make melanin in the skin to protect us from the UV rays in sunlight. (UV rays damage DNA in skin cells and can cause mutations that lead to cancer.)
But there is much more to melanin than tanning! For example, some forms of melanin are important for forming nerves in the brain and eyes.
This is why people with albinism have vision problems. They do not make enough melanins to hardwire their eyes properly.
People with fair skin still make plenty of melanin though. In fact, they make enough melanin that they have plenty for sight and all the other things melanin does.
Making Melanin is Hard
Making melanin is surprisingly complicated. It takes lots of steps.
Each of these steps is directed by a separate gene and each gene has the instructions for a unique protein. All of these proteins work together to make melanin.
Think about it like an assembly line in a factory. The 'workers' in this process are the proteins which are called enzymes. And each enzyme in the assembly line performs one step in the pathway of melanin production.
Let's get more specific and think about it like a factory that makes toy cars. This factory makes brown and yellow cars.
For darker skin, lots of brown and yellow cars get made. Let's say they make 70 brown and 30 yellow cars every hour. Everything is humming along.
For fair skin, fewer cars get made over all and many fewer brown cars get made. Now they're making maybe 10 brown cars and 20 yellow ones. They make more yellow cars than brown.
With albinism, no cars get made. Think of it like one of the workers not showing up for his shift. Now the whole assembly line shuts down wherever this guy was working.
Of course our cells don't make brown and yellow cars. But they do make brown and yellow pigments. And the same ideas with the toy cars apply to these pigments as well for skin color and albinism.
Dark or pale doesn't matter
When we step out into the sun, special skin cells called melanocytes react by making more melanins. Dark-skinned people tend to have bigger melanocytes, which contain a darker form called eumelanin (EM). Pale-skinned people have smaller, fewer melanocytes and they make more of a lighter, more yellow colored pigment called pheomelanin (PM).
Sun exposure causes melanocytes to step up melanin production. So everyone's skin starts making more melanin. Darker people make more EM, and pale people tend to make more of PM. But even though EM is darker and PM is lighter, both can do the job of protecting us from UV rays!
So pale-skinned people still make enough melanin to protect their skin.On the other hand, people with albinism can't make any melanin, dark or light. Their melanocytes have no pigment at all.
It's like having different colored beach umbrellas. A light or dark-colored umbrella would both offer protection from the sun, but not having an umbrella at all is a completely different problem.
Pale and dark skins evolved for different reasons in the past, but neither of them makes a difference to survival in the modern world. Albinism though, is still a genetic disadvantage, with many complications beyond just a light skin.
* The big exception is blue eyes which is due to a certain DNA difference that affects the OCA2 gene. This same gene is involved in many cases of albinism
Great video on understanding albinism.
Dr. Jyoti Madhusoodanan