TIL that due to a genetic bottle neck, 10% of the population of the pacific atoll of Pingelap has achromatopsia, i.e. only sees in black&white

genetic bottleneck ...as in inbreeding?

Yes. The difference being that it was due to circumstances that devastated the population.
Fun fact when Homo Sapiens migrated out of Africa it also experienced a genetic bottleneck since the group that left Africa was small in numbers. We can even see it in our DNA. Compare the DNA of a person with East Asian genes to the DNA of a Western European and you will find a higher percentage of similarities, than when you compare a West African’s DNA to that of an East African. Africa is genetically the most diverse region on the planet. Even though early Europeans mixed with the Neanderthals.
- Another cool fact: Chimpanzees are more genetically diverse than Homo Sapiens.
- so, what you tell me is that white people are inbred, neanderthal hybrids?
  
  that explains so much lmao
- As an european, this explains a lot.
- It amazes me how little population migration there has been in africa. Discrete groups remain isolated from each other for tens or even hundreds of thousands of years. Everywhere else, population migrations and genetic mixing has occured regularly.
20 survivors * 10 or so generations.

So inbreeding coefficient is around siblings for the entire population.

Complete achromatopsia is normally a very rare condition, and its prevalence on the island has been traced back to a population bottleneck in 1775 after a catastrophic typhoon swept through the island, leaving only about 20 survivors.

There are now 250 people on the island, and...

the disorder is now prevalent in almost 10% of the population, with a further 30% being unaffected carriers.

So ~25 people have it, and another ~75 are carriers.

"Total color blindness" does not mean "sees only in black and white"

Edit -
The reason I say this is that the phrase "only sees in black & white" in the title could easily be taken literally, making it sound like a simple black-and-white picture. While it's the most common and helpful analogy, colorblindness is more nuanced than that. I suggest a slight change in the title to offer more clarity:

TIL that due to a genetic bottle neck, 10% of the population of the pacific atoll of Pingelap has achromatopsia, i.e. total color blindness, like seeing in "black & white"

~Rant about people's reactions in this comment thread~

spoiler

This concept is clearly difficult to convey, I get that. However, I am disappointed that some reactions focused on criticism of my articulation rather than seeking clarification or offering alternative explanations. I tried an analogy using NULL to illustrate the conceptual difference, but that was also met with criticism focused on its imperfections rather than the concept I was trying to convey.

I have a range of close, personal experiences with colorblind people, and the conversation of colorblindness has come up frequently. I have also confirmed my understanding of the deeper nuances with optometrists and a neuro-ophthalmologist. My intention was simply to share my information, which I believed was the purpose of this community. It is disheartening to feel that my attempts to communicate were met with such negativity.

I have no idea what you're saying, but their receptors work in 1D instead of 3D color space. Dimensionality of black-white/brightness is 1D so the analogy is correct, they see in the same number of dimensions as black-white vision. We do not know how their brain actually interprets though.
- Actually, you've pretty much nailed what I've been trying to say.
  
  That's a good way of rephrasing my point. Calling it "black and white" is an analogy and not explicitly what they see. While we don't know how the brain interprets vision without comes from our perspective ("is my blue your blue?"), it's not "black and white" in the way we know it.
  
  The title just states it as if they explicitly see only "black and white" and I was just trying to point out the difference. It spreads bad information phrased like that.
I read through the article and followed the links and it still isn't clear to me exactly how much, if any color they can see.

Achromatopsia, also known as rod monochromacy, is a medical syndrome that exhibits symptoms relating to five conditions, most notably monochromacy.
- Well, it states "total color blindness" so, effectively none.
  
  My point is that when you have "total color blindness" it simply means you cannot effectively discern the difference of of color. That does not mean "black and white."
  
  For example, everyone has a blind spot in their eye where the optic nerve passes through the retina. This area has no photoreceptor cells, so there is a spot in each eye that cannot see. When you look through one eye and close the other, do you see a black void spot? Is it a blank white area? No. It's just... nothing.
Hey man, don't bring IEEE 754 into this unless you want to discuss how negative zero, infinity, NaN, and subnormals relate to the qualia of color perception.
- Look, it was not a perfect analogy. There's no need to be nitpicky and only focus on the fact the analogy is not perfect. I was grasping at straws to try to convey a difficult concept while I felt people were attacking me.

They are stuck in the early 20th century

Actually, we have some photographic proof that the 19th century was actually not black and white: https://en.m.wikipedia.org/wiki/Color_photography

Pingelap village