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Short answer Blue color is not only rare in edible organisms - Blue color is rare in both the animal and plant Kingdoms in general. In animals, blue coloring is generated through structural optic light effects, and not through colored pigments. In the few blue-colored plants, the blue color is generated by blue pigment, namely anthocyanins. The reason for ...


120

Although @AliceD's answer is a great simple demonstration of the rarity of blue in our natural world, there's likely a more nuanced/technical reason. Short answer Blue light was the most available wavelength of light for early plants growing underwater, which likely led to the initial development/evolution of chlorophyll-mediated photosytems still seen in ...


32

The first modern humans evolved about 200.000 years ago in Africa. When they lost their body hair (or at least most of it), they needed some other protection of their skin from the sun - otherwise they are prone to develop melanoma. Melanin is such a protection, and the rate of melanoma is much lower in dark skinned people. There is also a nice correlation ...


22

Easy: look at images of hairless cats. You will see they can be not only all black, but also grey, spotted, pink, and a few other rarer colors. Also, take an average cat - and shave for surgery: Note pigmented skin matching dark stripes.


19

According to wikipedia, "comparisons between known skin pigmentation genes in chimpanzees and modern Africans show that dark skin evolved along with the loss of body hair about 1.2 million years ago and is the ancestral state of all humans." This is several million years after after the time estimated for the last common human-chimpanzee ancestor, but at ...


18

The pigmentation of hairs is achieved by the follicular melanocytes (specialized pigment cells) at the base of the hair shaft. These cells produce the pigment which is subsequently transported into the cells which produce the hair and integrated into the hair matrix. Besides genetic reasons, there are two major ways of losing this pigmentation. First, as a ...


12

It isn't about heat but ultraviolet light. Melanin is the pigment that makes our skin colour whatever it is and in darker skin there's more melanin. Melanin dissipates UV, which otherwise would cause skin cancer as it introduces mutations into DNA. Melanin production is stimulated by UV so that's why tanning beds work, our body senses the danger and responds ...


11

The colour of human eyes is determined by the pigmentation present and the scattering of light. Variance in the colour and density of the pigments affects how light is absorbed and reflected causing the different iris colours we see. Wiki has a fairly comprehensive coverage on the topic so,I'll use a few of the wikipedia examples to explain how the ...


11

1) Is this plausible? It is absolutely plausible. His particular condition was called Vitiligo (as stated in your quote) and isn't that uncommon, albeit not usually as severe. Skin pigmentation expression changes over time, sometimes dramatically. 2) Is it likely to be an actual disease, or would there be so many mitigating factors that it is unlikely ...


11

The reason that chlorophyll is green is because it absorbs other colors of light such as red and blue, so in a way the green light is reflected out since the pigment does not absorb it. Because life might have been purple: It is possible that the very first life form to process light may have been purple colored. This would mean it was reflecting red and ...


11

Carrot (Daucus carota) is a biannual plant that accumulates massive amounts of carotenoid pigments in the storage root. The root of the carrot was not orange before domestication. Although the root of carrot plants was white before domestication, intensive breeding generated the currently known carotenoid-rich varieties, including the widely ...


10

I don't think, there is a precise answer about the evolutionary mechanisms, but "mechanically": mammals have principally just two types of pigments: eumelanin and pheomelanin, both of which have their color variants, but within a known range. Bird pigments, besides melanins, include carotenoids and porphyrins. Arthropods generally have carotenoids, melanins ...


9

Wild ducklings, like these baby Mallard ducks, are in fact typically only partly yellow: Photo by TheBrockenInaGlory via Wikimedia Commons, used under the CC-By-SA 3.0 license. While I'm no expert, I would guess that the mottled yellow-brown coloring of the juveniles is, at least partially, protective coloration, just like the somewhat similar pattern on ...


9

This source seems to suggest that cats' skin colour is determined by their fur colour, as the same genes expressed in the fur which produce the colours (melanins) are also expressed in the skin. The density of melanin can vary from one part of the body to another, down to patterns within individual hairs or gradients across skin, thus accounting for a wide ...


9

You're right that certain wavelengths of light are more capable of penetrating deeper depths of water. However, it turns out, blue light typically travels to deeper depths than all other visible wavelengths of light (and red light does not travel deeply at all). See my previous SE answer for more details about plant coloration due to this phenomenon. So ...


9

It is not that there are no blue foods, it is that the English language does not like calling foods "blue". There are no natural borders between "colors" in a colorspace, all colors we name (and learn to distinguish) are culturally defined. So, an important thing to recognize is that, a color somebody calls "blue" can be called "purple", "red" or "maroon" ...


8

A search of the Internet shows many anecdotal cases of people reporting their grey or white hair returning to their normal color.  Interestingly, many of these ancedotal cases begin by stating that their hair had turned grey or white at a young age (early 20s) before returning to it's natural color.  Finding a scientific explanation does not seem as easy. ...


8

Hair colour is maintained by a pigment called Melanin which also affects skin colour too. When the melanin content in your hair decreases, it turns grey and eventually white. Multiple factors affect melanin levels in your body. 1) age 2) Genetics 3) Diseases 4) Cell Stress You can read about them in a little more detail here. I cannot specifically ...


8

Hair color is not so simple as that. Most traits, especially those as complex as color, are controlled by many alleles at many loci. That's why there are different kinds of brown, blond, and red hair in the population. There is no "hair color gene." A fascinating paper came out a few years ago, identifying dozens of SNPs playing a role in hair and eye ...


8

The color of mammals is determined by the pigment melanin. More specifically it is the mixture of the dark brown to black Eumelanin and the red to yellow Pheomelanin. These pigments are made a specialized cell type called melanocytes, which are located in the hair follicles (when they pigment the hairs) and in the skin. Some animals (like mice) almost ...


7

It can actually be for both reasons and it more or less depends on the age what happens. The pigment of the hair is produced by pigment cells (the melanocytes) in the hair bulge and is then integrated into the growing hair (image from here). The pigment melanin produced by these cells can be destroyed by reactive oxigen species which then leads to grey hair ...


7

The genetics of pigmentation is relatively complicated, as the pathway for the pigmentation (regulation of the pigment production, ratio between the melanins, maturation, trafficking and distribution of the melanins from the melanocytes to other cells) is quite long and also subject to different regulations. All the mutations found to date (at least to my ...


7

The yellow color comes from the accumulation of Bilirubin in the body. Bilirubin is a breakdown product of hemoglobin (contained in erythrocytes, also known as red blood cells, and responsible for the oxygen transport in the body). (This is also the reason why bruises get colored, as the blood which was released into the skin gets removed.) As erythrocytes ...


7

Pure nicotine is a yellow colored liquid (although some sources say it's a clear liquid.) "Tar" is a complex sludge that is also yellow-brown. So it's difficult to distinguish 'nicotine stain' from a 'tar stain' based on visual inspection. Let's go to other considerations. The concept of a 'stain' implies that simple hand washing doesn't remove the ...


6

Surprisingly, it is indeed possible! But, the fact is that the actual process is a bit more complex and might actually require more compounds along with cysteine to give such effects in living beings. First of all, see this image1: As is clear from the diagram, GSH (glutathione) is also a factor for pheomelanin production, along with cysteine. Another ...


6

Blue coloration in animals is caused by structural color rather than blue pigments. In the case of vervet monkeys and other mammals studied this is due to collagen fibers in the skin being arranged with a regular spacing that results in blue wavelengths constructively interfering while other wavelengths destructively interfere1. This "news" article in ...


5

There is only one main "coloring" agent, or pigment, in the eyes. That pigment is melanin. To a much lesser extent, at least in health individuals, you can have lipofuscin produced which gives a golden-amber color to the eyes. It should be noted that lipofuscin is most likely produced because of oxidation damage/stress in your eye, and not ...


5

Short answer Tar deposition is the cause of the yellow cigarette stains. Background Both tar and nicotine cause yellow to brown staining. Although nicotine itself is colorless/white, it turns yellow upon exposure to air. In a study on cigarette stains, the author speaks of tobacco-tar stains, implicitly acknowledging it is tar and not nicotine (John et ...


5

I rather would say that the lack of North/South Symmetry in pigmentation is that we forget how quickly human beings have spread. In prehistory, people have come to populate every continent over perhaps the last 60,000 years. While in that time its clear that several mutations have popped up to influence skin color, they are pretty rare compared to the ...


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