Did Skin Color Evolve as an Adaptation to Sunlight Intensity? - dr d adamo skin care product review
It is highly variable all over the world. .
However, in the past 500 s, the huge global migration of human skin color groups has led to vitamin D deficiency, which has caused rickets disease and osteoporosis problems, leaf acid deficiency that causes birth defects and reproductive problems.
Groups of various skin tones no longer live in areas where their skin adapts.
This is combined with the trend of people staying indoors, using sunscreen and reducing sun exposure means that various skin tone groups must take various actions to reduce the risk of sun exposure and health problems caused by skin tone.
Human skin color ranges from the dark brown of some Australians, Africans and Melanesians to the almost pale yellow pink of some northern Europeans.
The skin color of different groups of people is often mixed instead of real black, yellow, white or red, and these commonly used skin color terms are often incorrect and misleading. --------------------------------------------Fact -
Skin color is mainly determined by a pigment called melanin.
People with light and dark skin have the same pigment.
However, there are two forms in the first place.
People with shallow skin will produce more melanin, while people with deep skin will produce more melanin.
In addition, individuals differ in the size and quantity of melanin particles.
These aspects tend to be more important in determining skin tone than the kind of melanin produced.
In lighter skin, the color is also determined by red blood cells in the blood near the skin. ---------------------------------------------Tanning -
For people with light skin, it is more obvious that the skin is tanned, but the dark brown skin will also be tanned because it is exposed to the sun for a long time.
Sunlight stimulates the release of MSH in the lower brain gland (melanin cells-
Stimulating hormone ).
This hormone enters the melanin cells through the blood, making it produce more melanin.
Since the lower brain gland is connected to the visual nerve (the nerve in your eyes makes you feel the light), wearing sunglasses will make you black.
The tanning reaction strongly indicates that skin tone is very important in humans and they have developed ways to change skin tone in response to sunlight exposure.
This strongly suggests that more persistent skin color changes around the world are equally adaptable, and are a genetic feature that has been selected to provide an advantage for a variety of skin tones with different sun intensity in different regions of the world.
Prior to the massive migration of the global population in the past 500, dark skin tones were mainly concentrated in the southern hemisphere near the equator, and light colors gradually increased from the equator to the north, as shown in the figure.
There is a strong correlation between skin color distribution and sunshine intensity.
Most people with dark skin initially live within 20 degrees of the equator.
Most of the lighter-skinned people live in the northern hemisphere, 20 degrees north of the North latitude.
Related to this distribution is the highest UV intensity at the equator where the sun is stronger.
In contrast, people close to the poles in a cold climate usually have mild pigmentation.
The relative intensity of solar radiation is the main reason for this distribution pattern.
There are some exceptions to this distribution.
Inuit live near the Arctic, but their skin is darker.
This seems to have something to do with their diet because they have a rich amount of vitamin D in their diet, making their skin darker, and getting less vitamin D from sunlight.
How are these skin color patterns formed?
The Neanderthals may have a light complexion and are more adaptable to the cold climate at the end of the last ice age.
It is widely believed that the skin of early modern people who developed in Africa is black, and they migrate from the north and east to live in other parts of the world.
Why do these populations have lighter skin tones as they move north?
The reason seems to be related to evolution and natural selection in response to changes in UV radiation, as well as inheritance of gene mutations.
See more details about this later.
Why is black skin an advantage in early humans?
It was suggested that as early humans move from forests to the hot, open environment in Africa to find food and water.
On the open plains, they face major challenges in keeping cool.
The favorable adaptation is to increase the number of sweat glands on the skin and reduce the number of body hairs.
Hair is much less, sweat can evaporate more easily and cool the body better. But this hair-
Skin reduction is a potential problem as it is exposed to intense sunlight in areas near the equator.
The adaptive response is to choose a skin that is permanently dark to prevent destructive light from the sun.
Although ultraviolet rays can cause skin cancer, this cancer occurs after the birth age and is therefore unlikely to be selective.
Evolution and natural selection have a significant impact on reproductive success, so adaptation is closely related to other health effects (or perhaps appearance), thereby improving reproductive success for individuals with dark skin.
At least six hypotheses for darkening the skin were proposed: (1) reducing the sun damage of sweat glands and skin blood vessels, (2) preventing skin cancer, (3) preventing excessive production of vitamin D, (4) camouflage, (5) better prevention of microorganisms, (6) protection of important processes and essential molecules in the blood related to reproductive success.
UV rays are known to penetrate lighter skin and destroy folic acid molecules, which reduces reproductive success for both men and women.
UV radiation protection-
In tropical areas, people with darker skin tones are naturally chosen, especially in non-forest areas where solar ultraviolet radiation is usually stronger.
Melanin is a natural shield against ultraviolet radiation.
The development of tanning reactions demonstrates the importance of skin tone in preventing the effects of sunlight exposure. Vitamin D -
If melanin provides a complete barrier against ultraviolet radiation, it will be harmful.
In order for the body to produce vitamin D, a certain amount of ultraviolet radiation (short-wave ultraviolet rays) must enter the outer layer of the skin.
About 90% of this vitamin is usually synthesized by cholesterol in the skin and kidneys.
Like the chemical precursor.
The remaining 10% comes from foods such as egg yolk, fish fat, such as cod liver oil.
Moving to higher latitudes far from the equator means a decrease in the intensity of sunlight.
People with dark skin may have vitamin D deficiency at higher latitudes because their skin absorbs most of the ultraviolet radiation.
Many Americans with black skin have shown a high incidence of osteoporosis and other problems caused by vitamin D deficiency in adults.
On the other hand, people with shallow skin in the tropics may show signs of excessive vitamin D.
Folic acid (folic acid )-
Excessive UV penetration through the skin may destroy folic acid (or folic acid-
A B vitamin) that flows through the blood vessels under the skin, which may lead to anemia.
DNA replication in splinter cells requires folic acid, and the absence of folic acid may affect the production of sperm cells.
Pregnant women with folic acid deficiency have a higher risk of miscarriage and baby tube defects.
The health authorities recommend that pregnant women take folic acid supplements to reduce this risk.
The sources of folic acid include brussels sprouts and green leafy vegetables such as spinach, bananas, potatoes, strawberries and beans.
Folic acid has been added to some bread, pasta, and cereals, and there are labels to indicate this.
It seems that the ability to produce melanin has been chosen in early humans as it helps to preserve folic acid in the blood, thereby increasing reproductive success.
This will benefit individuals with darker skin in the tropics, but this effect will be reduced in areas with higher latitudes.
It may have a significant impact on the perception of skin tone, but this cannot be estimated.
In traditional African societies, light skin is often considered unhealthy.
The naturally occurring albinism is rejected.
Skin tone preference may affect reproductive success.
Even today, skin color preferences vary from culture to culture.
Historically, many cultures favor the light skin of women, and many young women always use umbrellas when they go out in the sun.
Incidence of MS
There seems to be a strong correlation between the amount of exposure to sunlight in children and whether they will develop into multiple hardening in adulthood.
Most MS occur in the temperate regions of the world where the sun is not strong.
Children who grew up in subtropical and tropical areas, regardless of their ethnic origin, rarely develop MS.
For those who moved to the far north or south after the age of 16, this protection seems to continue.
These processes are responsible for protecting the skin from MS and its possible relationship with the skin color is unknown.
Why is light skin an advantage in areas with higher latitudes?
Melanin in dark skin provides natural protection for tropical residents from a variety of harmful effects of ultraviolet rays.
Ultraviolet radiation can destroy folic acid, lead to a lack, and cause miscarriage and deformity of the fetus.
However, ultraviolet rays must penetrate the skin in order for the human body to make vitamin D, which is necessary for the body to absorb the calcium needed for strong bones.
This delicate balance associated with skin tone seems to explain why groups migrating from the equator to areas with less sunlight adapt by developing lighter skin tones.
In areas with higher latitudes, natural selection prefers lighter skin as it allows UV rays to penetrate and produce the necessary vitamin D.
Because it prevents the lack of folic acid and other problems exposed from ultraviolet rays, naturally choose to prefer dark skin at the equator.
A major exception to the connection between skin color and equatorial distance is the Arctic groups, such as the indigenous peoples of Alaska and Canada, who maintain darkness
Skin even in low UV areas.
People in these coastal areas eat foods rich in seafood that provide an alternative source of vitamin D.
In the summer, they reflect a high level of ultraviolet rays from the surface of ice and snow, and their dark skin protects them from this reflective light.
There is evidence that these groups have developed vitamin D deficiency in modern times as Western diets change.
While suntan skin is the most obvious for people with light skin tones, dark brown skin can also be sunburned with prolonged exposure to the sun.
Some Europeans have lost their ability to tan.
Their skin is not tanned, but tanned.
This is caused by a mutation that causes a defective skin protein that interferes with the production of melanin.
They are not suitable for tropical and subtropical areas that are more prone to sunburn and skin cancer.
The same is true for patients with albinism.
Researchers working on the zebra fish found a gene that interferes with the production of melanin required for dark stripes when mutations occur.
The team scanned human DNA to see if similar genes were present.
They found almost the same genes in humans, dogs, cattle, chickens and many other species.
When studying the genomes of the world's four major ethnic groups, the researchers found that only white populations from Northern and Western European ancestry had a mutant version of the gene.
There is no such mutation in the Asian group.
This mutation seems to cause 1-
Third, the loss of pigment causes the skin to become white.
Other mutations may also be the cause.
In conclusion, as with many other evolutionary changes, adaptive changes in skin tone seem to have developed due to the combination of genetic mutations and natural selection of skin tone changes.
People with dark skin living outside the equator, with relatively weak solar radiation most of the year, have to deal with the potential problem of vitamin D deficiency, this may lead to rickets disease in children and osteoporosis in adults.
In the 1900 s, people took cod liver oil to prevent the high incidence of rickets disease caused by people staying indoors and rarely exposed to the sun.
In the United States and other countries, to prevent these problems, vitamin D and A are now commonly added to milk and other foods.
There have been recent reports of malnutrition in American children. S.
Georgia is a high-incidence disease, especially among African-Americans.
This previously rare disease caused by vitamin D deficiency seems to be mainly due to three things: drinking a milk substitute that does not contain vitamin D, failing to replenish breast milk, and insufficient sunlight.
Pregnant women need to add folic acid in their diet, which is a further reaction to light skin people living in areas where excessive UV exposure destroys folic acid in their blood.
Some researchers have also expressed concern that the use of sunscreen and exercise to prevent people from sunbathing may also lead to vitamin D deficiency in people with lighter skin tones.
Clearly, the modern migration of the population has offset the adaptation of the color of the skin, which is intended to allow people to live at different latitudes.
Action must be taken by various groups to overcome the problems caused by these immigrants and modern lifestyles that affect sun exposure and increase the risk of various health problems.
There is a lot of research on this interesting topic. Â© janderson99-