Some foreigners have blond wavy hair, and some have short black hair curled up on the scalp. In fact, hair color and skin color are determined by melanin. If the amount of granular melanin contained in the hair cortex is greater, the hair becomes darker. If the hair medulla also contains melanin, the hair color is even darker; on the contrary, if the melanin is distributed in a solution state, the hair is often reddish in color; and the golden hair contains a lot of melanin in solution Sake. The hair color in our country is mostly dark brown and black.
Hair color also often changes with age. Generally speaking, after entering middle age, the gap in hair tissue increases, the granular melanin gradually decreases and disappears, and the hair gradually turns yellow. When there is air between the cortical cells, the hair becomes white. It has been reported that at the age of 60, about 50% of people have gray hair; at the age of 75, the gray hair reaches 70%; there is no obvious difference between men and women.
In addition to changes in age, hair color is also affected by health conditions, sunlight, and climate. For example, severe malnutrition and disease can make hair white early; excessive worry and nervousness can also make hair white, even faster. As for some people with early gray hair, it is mainly related to genetic qualities or mental state.
Since hair color, like skin color and eye color, is determined by melanin, there is a close correlation between the three. Worldwide, light-skinned people are often accompanied by light hair and eye color, while dark-skinned people are often accompanied by dark hair and eye color, such as the Nordic, the skin is white, the hair is golden, the eyes It’s azure blue. And black people, regardless of skin color, hair color or eyes are black.
Human hair is not only of various colors, but also of different shapes. However, in anthropology, it is mainly divided into three major types, each of which is divided into several subtypes: one is straight hair, including hard straight hair, flat straight hair, and microwave hair; the other is wave hair, with wide wave hair, Narrow wave hair, curly wave hair; third is curly hair, there are thin curly hair, loose curly hair, tight curly hair, loose spiral hair and tight spiral hair. The last two subtypes in curly hair, namely loose spiral and tight spiral hair, are often entangled in a cluster, so that the scalp between the small clusters is exposed, so some people list this type of hairstyle separately It is a kind of wool-like hair.
Hair style and hair color are one of the important ethical characteristics. Generally speaking, yellow people have more straight hair, white hair has more wave hair, and black people have more curly hair. For example, most residents of Central Asia, North Asia, East Asia, and American Indians have straight hair; while the Eskimos in the Arctic have the straightest hair. Europeans are more frequent. Australians and some residents of South Asia and Southeast Asia are also part of Bofa. Belonging to curly hair are black Africans and residents of New Guinea and Melanesia. Wool-like hair is unique to Bushmen and Hottent.
Chinese have the most straight hair. Especially the northerners rarely see the waves; but the southerners can see a few waves, and the more southward, the more waves.
How are these different hairstyles formed? It turns out that the shape of the hair shaft is mainly formed in the hair follicles in the skin, which is determined by the shape of the hair root. Straight hair roots are straight, wavy hair roots are slightly curved, and curly hair is curved like a saber. After the head emerges, it still maintains its curved state in the skin, thereby forming different hairstyles. However, the cause of the hair root bending has not been fully clarified so far, and some people think that it mainly depends on the hereditary inheritance.
The length of the hair is related to the hairstyle. Straight hair is usually the longest, often up to more than 1 meter; curly hair is the shortest, especially the spiral hair is shorter; wavy hair is in between. In the same ethnic group, women’s hair is often longer than men’s, especially in the Bohai ethnic group, this difference is more significant.
Hair can grow about 0.3 mm in a day and night, which is related to various factors such as race, age, nutrition, mood and health, and season. For example, it is hot in the summer and the hair grows faster; in winter it is cold and the growth is slower. But no matter what kind of hairstyle, the hair will not grow endlessly, and its life span is about 2 to 5 years. However, there are a few women whose hair can grow particularly long. For example, Hiroko Yamazaki, Tokyo, Japan, has never cut her hair since the fourth grade of elementary school. At the age of 35, her hair is 2.32 meters long, and her hands are stretched out and her hair is still on the ground. She wash her hair once a week, it takes half a day and half a bottle of shampoo. When you go to bed at night, you should put your hair on the pillow.
The thickness of the hair can directly affect the hardness of the hair. Generally, the harder the hair, the larger the cross-sectional area. Straight hair is the thickest, up to 0.1 mm; wave hair is the second, 0.08 to 0.09 mm; curls vary greatly, but most are thinner than wave hair. Straight hair has a round cross-section, wave hair is a slightly flat oval, and curly hair is long and flat. Some people think that thin and soft hair is easy to fall off, and hard and thick hair is easy to turn white.
As for the density of the hair, it is related to the thickness. The thinner the hair, the denser it becomes. In terms of the number of hairs per square centimeter, among the major races, white people are the most, black people are second, and yellow people are the least. Some people once calculated that the number of hairs per square centimeter is 408 for Italians, 236 for Sudan, 238 for Japanese, and 224 for Chinese.
In addition, human hair has different spins. The difference in hair rotation is the number, direction, and location of the hair rotation, the distance between the center of the hair rotation and the apex of the head, and the angle formed by the connection between the head apex and the hair center and the median line of the head.
The thick hair on the head is one of the characteristics of human beings. But on the other hand, after entering middle age, not only will the hair gradually turn white, but also due to the shrinkage of the hair nipples, the hair will obviously reduce and gradually become bald, which is also one of the characteristics of human beings. It has been reported that about 80% of people 60 years old develop baldness; over 75 years old, the rate of baldness exceeds 90%. However, men with more baldness usually begin in middle age from the top of the inside of the temples on the front of the head, and then expand to the back and sides. And there are more white bald people, black people are only one-tenth of white people, and American Indians are even less.
