ttoo, sexual excitement… Miracles happening in ‘there

In. It would have been much better to take the stories in the endnotes as text and write them twice as thick. Rather than stopping the explanation at the point where the readers are barely able to understand and curious to arise. There were questions left to me too. The author argues that skin color is only an adaptive trait and cannot be used as a basis for racial classification, but race in the sense that ancestors are the same group exists, and skin color is one trait, so it may be correlated with other traits. Isn't it something you don't know?
 It would have been nice to introduce more meticulously the genetic studies of the relationship between skin color and race. Not only that. So I am curious about whether cosmetics that fill collagen are effective or not, by what mechanism the sunscreen exerts protection, and curious about the skin graft technology that has been described in a tantalizing manner. But I don't want to disagree with Nature's comment that "this book tells us everything we want to know about skin." Rather than worrying about natural wrinkles or sunburn, the information that the book tells you is not light in that this versatile cover lets you admire the important functions it performs constantly.  I have a tattoo. It is a simple vine pattern called a tribal pattern. Will it be about 15 centimeters wide and 6 centimeters long? The reason I can't say it exactly is because it is on the back waist. It can only be seen in the mirror. So, I am not usually conscious. However, the memory of this tattoo is vivid. While the tip of a disposable needle pokes deep into the skin and pushes the paint in, I, lying on the bed, focused my mind on the novel with a handkerchief in my mouth so as not to make any noise. If that worked, the practitioner said, encouraging me to be quite patient. "Is it okay to wrap a tiger with Resume?"

Now I can't even remember why I wanted to get a tattoo and inkeeze products. Both my family and my friends responded insignificantly. However, there were people who sometimes looked strangely. They asked if it would be burdensome to carve a trace that lasts a lifetime. But that's wrong. Nowadays, you can erase any number of times with a laser. Still, it is difficult to engrave the name of your lover.... It's only half that I'm worried about others' glares. Unless even Marilyn Monroe is inscribed on the biceps. In my view, such resistance is an instinctive response rather than a rational response with a specific reason. Even in these days, when cosmetic plastic surgery has become widespread and the resistance to body modifications has declined endlessly, people still feel that painting on the skin will irreversibly change them.

Maybe that's because the skin is the body organ that best represents the self. If you think about it, it really is. When we say we see the body, we are actually seeing the skin. The internal organs, muscles, nerves, tendons, and fat contained in it will not be seen once in a lifetime. Prior to the advancement of medicine, the condition of the organs in the body could be known only through signs exposed to the skin. In the case of an average adult, skin weighing 4 kilograms and reaching 0.6 peon of surface area is the largest and heaviest organ in the body. As poet Hwang Jib-woo said, I'm the one contained in the "skin bag that became completely old and comfortable", and "the skin I live in" is coming soon, according to the title of the film directed by Pedro Almodovar

Thanks to this, we are too familiar with the idea that the skin is an organ of the human body, but there is no other shell that is so surprising. The skin is a sack that holds the body to maintain its shape, is a barrier that prevents foreign matter such as rain from seeping in, and a protective shield from attackers such as insects. The skin cools the body by sweating, makes it feel to the touch, and blocks ultraviolet rays by naturally tanning in the sun. How great is the performance again? Even if we are soaking in sea water, it does not swell like a balloon, and because it is constantly replaced with new skin, unlike internal organs, we do not fall into a dysfunction state. You can do all of this and still be less than 4 millimeters thick! (The skin is divided into two layers: the epidermis on the outside and the dermis on the inside. The thickness of the epidermis is 0.4 to 1.5 millimeters, and the dermis is 1.5 to 4.0 millimeters.) In addition, the skin is social, cultural, and political. Since the early days of history, humans have expressed their sense of belonging to the group by painting on their skin. The oldest human skin discovered so far is from a frozen human ‘Shout' who lived in the Neolithic Age 5,000 years ago, and there are small traces of tattoos on his back. And skin color was used as a basis for human discrimination against humans. Skin is also an identity. Of course, the heart, the cerebral cortex, the lumbosacral muscle, and the appendix are all important (well, should the appendix be canceled). However, beyond biological, the only social, cultural, and political institution is the skin. 

As you may have guessed, the reason why I suddenly fell into a skin tribute is because I read a book that praised ‘biological, social, cultural and political skin'. It is Skin written by anthropologist Nina Zablonsky (subtitle is ‘The Secret Hidden in Skin Color'). Contrary to the title, this book doesn't just deal with skin color issues. It covers all the topics I have listed above. However, since the author has studied the evolution of skin color for a long time, this issue is covered in the most detail. Then, what is the ‘secret hidden in skin color'? It is a fact that skin color is an attribute that humans evolved through natural selection in order to adapt to the environment (mainly ultraviolet rays). It sounds natural enough to collapse at first glance. However, it is of great significance to clearly define this attribute as an adaptive trait, which once carried a erratic meaning out of essence. 
This is because the lighter and darker skin has nothing to do with human superiority and inferiority. The author's conclusion is that the skin color only reflects the UV index of the environment in which an individual lives (to be precise, his ancestors lived). The evidence is multifaceted. First of all, the result of predicting skin color distribution around the world based on the assumption that the more UV exposure is, the darker the skin is, and the result of measuring the skin color of indigenous peoples is exactly the same. 
There is also a biological basis. The human body should not get too much ultraviolet rays contained in sunlight, but it should not get too little. Long-wavelength ultraviolet rays are a headache for destroying folic acid and DNA, which are important for reproduction, but short-wavelength ultraviolet rays are essential for the synthesis of vitamin D, which functions critically in the body's calcium metabolism. Therefore, it must be balanced exquisitely to prevent vitamin D deficiency while preventing damage from ultraviolet rays, and melanin pigment, a natural sunscreen agent, plays a role. That is, in the equator where there is a lot of ultraviolet rays, it is advantageous to have a lot of melanin pigments, and it is advantageous to have less melanin pigments toward the polar regions with less ultraviolet rays. The authors emphasize that both folic acid and calcium are important substances for reproduction. That is why natural selection had sufficient motivation to exert adaptive pressure and change the amount of melanin pigment. This theory can also explain the difference in skin color between men and women. Women need twice as much calcium as men during childbirth. Therefore, they should have better vitamin D mobilization ability than men, and because of that, the skin became lighter to absorb more UV rays. However, when it comes to skin, what deserves more attention than color is sweat. The author said, "If a large number of sweat glands do not cool the body by sweating a lot, we (…) could not have evolved our ability to run fast, have high-performance brain activity, and live a clear mind in broad daylight even in hot areas. No one wrote a poem or song praising the greatness of sweat, but sweat is well worth it," he solemnly declares.

According to evolutionary biological studies, humans' distant ancestors would have had a pale skin color, had a lot of hair, and would not have sweated much (chimpanzees and other modern primates close to humans also have light skin). However, as humans traveled through the open grasslands to hunt and gather, and as the steam sprung up and rotated the large brain, a more efficient cooling method became urgent. The result was a lot of sweat, hairless skin (soft hair rather keeps body temperature constant, but sweaty hair increases body temperature limitlessly), and dark skin color (no hair, so I had to respond to ultraviolet rays in a different way) (But why did only the hair remain on the head? Check it out in the book). 

In addition to UV protection and cooling, the skin has many roles. So, the book quickly moves on to the next topic. A sense of touch that goes beyond gathering information about the environment and even builds an emotional bond between people (think erogenous zones). An emotional function that unconsciously reveals a mental state through cold sweat or flushing (think a lie detector). It functions as a canvas and billboard for body art such as makeup, tattoos, and piercings. And although this book "is an informative book, not an advice book", it must also address practical issues related to skin. So, it introduces various skin diseases from spots to skin cancer, and also introduces various cosmetic techniques from tanning to Botox.