Why did primitive people lose their hair?

The degeneration of body hair is the biggest difference in appearance between humans and other primates. Since human evolution, except for the thick hair on the top of the head, most of the hair on other parts of the body has faded. And as age increases, the hair on the top of the head will become increasingly thinner. What is even more sad is that with the pressure of life, With the increase in hair loss and bad habits such as staying up late, the post-90s generation in their 20s have also begun to suffer from hair loss. The role of body hair is obvious. It can resist cold and protect the skin. The main activity areas of humans are in the tropics and temperate zones. In temperate zones, they will experience long winters and need body hair to protect themselves from the cold. So why has human body hair degenerated? One million years ago, humans began to use fire. At that time, humans had already lost their hair. Could it be that after humans had clothes, they no longer needed hair, and then their hair naturally faded away? Actually no, because hair falls out earlier than humans wear clothes. In fact, this issue has not been studied clearly yet, but there are various hypotheses. The reason for this view is that about 7 million years ago, part of the African continent was submerged by sea water. Monkeys living on land had to adapt to life in the water. In order to reduce resistance when swimming, their hair degenerated. I personally don't agree with this view. Although hair loss can reduce resistance, there are also many long-haired animals in the water. For example, sea otters have thick hair, and cows can swim and have fur. The sea water is cooler, and having fur is good for keeping warm, so I personally feel that the aquatic ape theory is not reliable. Humans shed their hair to better dissipate heat. I personally think this is more likely. Although humans now have footprints all over the five continents, the earliest human ancestors mainly lived in the tropics, where the weather is very hot, and humans are essentially tropical animals. When human ancestors walked upright, the area exposed to the sun was larger. In order to increase heat dissipation, the thick hair gradually degenerated. In fact, many animals now shed their hair due to high temperatures. In my hometown of Inner Mongolia, at the end of spring and the onset of summer, a large number of cattle and sheep will automatically shed their thick hair over the winter. Before winter comes, their hair will grow again. long. However, human hair does not grow back after it falls off. There is also a view that it is to prevent parasites. Personally, I feel that this may be the reason, but it is not the main reason. Why did only humans lose body hair during evolution, but not other primates? This is one of many reasons to question evolution. The key is that this issue cannot be proven directly, because the component of hair is a protein, which cannot be preserved for a long time like bone fossils. However, in molecular biology research, some indirect evidence can prove that human beings have degenerated body hair, which is consistent with the theory of evolution. Below I will Have a chat. Body hair is very important for survival, and among mammals, most animals have body hair. The hair of a male lion is an aesthetic feature. Animal body hair can prevent skin bumps, scratches, and bites to a certain extent. Food energy is not easy to obtain. Body hair can reduce heat loss and protect the body from severe cold, preventing the fragile skin inside from being burned by ultraviolet rays. All this seems to tell us that if the theory of evolution is correct and humans really evolved from primates, then why do humans shed their body hair, a trait that is beneficial to survival? Why are humans the only primates without body hair? In the theory of evolution, the ultimate mission of humans and animals is to survive and reproduce. The main features that distinguish humans from animals are "large brain capacity" and "walking upright on two feet", which are inseparable from the fact that humans have lost their body hair. There are several main reasons for the increase in human brain capacity: First, gene mutation is the most important condition: for example, MCPH1 (brain development), FOXP2 (language) and other genes. Natural selection: In the process of reproduction, the fittest survive, and the more "intelligent" humans are constantly selected from the best for reproduction. Energy: High-protein meat is the source of nutrition for humans to increase their body size and expand their brain capacity, and meat comes from hunting. Basics: Humans can support their heavy brains by standing upright. A study published in the Proceedings of the National Academy of Sciences shows that the energy consumed by humans walking upright is only one-quarter of the energy consumed by chimpanzees walking on all fours.

In an environment lacking food, saving energy is more conducive to survival, so humans have been evolving in this direction. This evolutionary result extends to two advantages: the freed hands can use stones to dig plant roots, and can walk farther and longer, which is more conducive to survival. Very few animals can travel long distances. Cheetahs, tigers, and lions have strong explosive power, but short distances. This is because they have thick hair and no sweat glands on the surface of their bodies, so they cannot dissipate heat. The accumulated heat in their bodies suppresses the distance of movement. If they force a breakthrough, they will fall to the ground with "heatstroke". Humans do not have sharp claws, teeth, or a strong physique. If they want to obtain meat, only a few people will track down some aggressive smaller animals (or animals that run away when they see people). Because many animals cannot store a large amount of energy in their bodies and need to eat frequently, through constant tracking, the animals cannot replenish energy under pressure. There are also a large number of animals that cannot run a "marathon" at all due to energy and heat dissipation, so they chase their prey. Exhaustion was the main skill for humans to obtain food at that time. This hunting method continues to this day. In the BBC's "The Complete Biography of Mammals", the production team followed the primitive tribes in Africa in a car and chased antelope and other prey for more than 30 kilometers until the prey could no longer run away. , in close capture, if it is too far away, it is not cost-effective for the indigenous people. On the hot East African savannah near the equator, hunting was not an easy task for the early "fur-clad" humans (orangutans). In order to survive, humans experienced major choices. In the long history of evolution, genetic mutations are random, but the pros and cons are determined by the environment. For example, there are 40 million carriers of sickle cell anemia worldwide, resulting in at least 100,000 deaths every year. This is caused by a genetic mutation related to hemoglobin (HbS), but this fatal mutation can protect against one of the world's deadliest diseases - malaria, so carriers survive and pass on the fatal gene from generation to generation. . When hunting, the sweat glands on the hands and feet are not enough to discharge the heat generated by the human body, and the thick hair is not conducive to the evaporation of sweat and the loss of heat, so the selection of prey is limited. Because it needs to stop frequently to rest, it often loses track of its prey and cannot get food. During the evolution process, due to accidental genetic mutations, human sweat glands began to spread all over the body, and body hair was shortened and replaced with shorter hairs, so that heat can be quickly discharged from the body and more suitable for obtaining energy. Such genetic combinations stand out in the survival of the fittest. Due to insufficient evidence, the sequence of evolution of sweat glands and body hair is currently unknown. Although we mentioned at the beginning that body hair is also beneficial to survival, just like sickle cell anemia, the advantage of body hair and the acquisition of food are more beneficial to each other, and the evolution of humans later made up for the lack of body hair. For example: genetic variation allows skin pigmentation to resist ultraviolet damage, and access to more food sources can make up for the energy loss of the human body without hair. However, in the hot African grasslands, insulation and cold protection are not a big problem. During the evolution of a species, survival is the first goal. When there is a choice in the direction of evolution, the species will develop in a direction where it is easier to survive. Because the direction depends on the speed of the species on the survival track, and the track is the natural environment. From the perspective of the entire evolutionary history, the reason why humans are the only species of primates that do not grow body hair is because humans and other primates have different evolutionary directions. We cannot find fault between species of the same order, just like although bats are mammals, they can fly and fly better than ordinary birds. In primitive times, the living habits of human beings were similar to those of nature and animals, and because we humans did not have the same sharp claws and fast running speeds as animals. Therefore, most humans live in groups, and when they eat meat, animals tear the meat from their prey, not to mention that we humans have all kinds of clothes to cover our bodies. At this time, body hair plays the most important role. It plays an important role in not only covering our bodies but also keeping us warm.

Compared with ferocious animals, human bodies at that time were relatively small, but humans continued to use the wisdom in their minds to create miracles one after another, and even created new civilizations. With the changes in the living environment, humans have only retained a small part of their hair during the evolution process. For example, fine hair can maintain the ecological balance of the human body, and can protect from the sun. The hair in the armpits and iliac fossa is good for perspiration and protection against bacteria and insects. Parasitism, these are beneficial to human health. The hypothesis of "heat dissipation theory" and "water ape theory", "heat dissipation theory" refers to the fact that in the process of evolution, in order to adapt to the environment, we humans choose to shed excess hair on our bodies to achieve the effect of heat dissipation. The "water ape theory" refers to the fact that humans in the primitive period did not always live on land. They lived aquatic and terrestrial lives. Then, at this time, they needed to shed excess hair on their bodies to make it easier. purpose of action. In addition, the living conditions in the primitive period were harsh. Apes could not avoid long-term exposure to the sun. The thick body hair could protect them from the sun in most cases. Therefore, at that time, hair was regarded as a barrier. However, nowadays, hair is no longer needed to avoid sun exposure. , clothes have replaced hair. The emergence of clothes can protect us from the sun in summer and keep out the cold in winter, so hair naturally degrades during long-term non-use. In fact, there is no very definite answer to why humans lose most of their body hair. We need to slowly discover these. The earth is not always like spring all year round. Some places are cold all year round. At this time, the fur of animals is their "sharp tool" for keeping warm. When the temperature is high, they will also shed their hair to dissipate heat. These are retained by natural selection during the evolution process. Darwin believed that certain changes in the environment are likely to cause changes in certain habits of animals, and changes in habits will cause certain organs to develop in a certain way due to frequent use, and conversely, other organs will develop if they are not used frequently. Degradation is highly likely to occur, and directional mutations may also occur under environmental influences. In layman's terms, it is an acquired trait that can be inherited from generation to generation. In general, if the environment changes in a certain direction, as well as the use and disuse of certain organs and acquired inheritance, these small mutations will gradually accumulate, causing certain changes in organisms, and we humans From ancient apes to ape-men and now is the best example. The hair of the human body is of course too little compared to that of animals, which has also become an obvious difference between humans and animals. But biologically speaking, humans are primates and are essentially the same as other animals. What causes such differences? Most animals are covered with thick body hair. In ancient times, humans at that time, which should be called the ape-man era, were still living a life of eating hair and drinking blood. They had to go out to hunt and co-exist with beasts, and the living conditions were harsh. If you often travel in the wild, you will inevitably be exposed to the sun. The protection of thick body hair can avoid sun damage to a large extent. Although the apes at that time were all thick-skinned and thick-skinned, their thick hair was at least a barrier. The Living Environment of Ancient Humans Secondly, millions of years ago on the earth, there were many more ferocious animals than apes. Going out to hunt and capture animals larger than yourself was a very risky thing. The cover with hair can enhance the camouflage effect and make it difficult to detect. We can imagine that if modern humans had thin skin and tender flesh, if they were left in ancient times, they would have been spotted by natural enemies a few kilometers away. In addition, they could not run well, so they would have been regarded as prey. It has been difficult to study at what point in the millions of years of evolutionary history humans began to gradually wear clothes. The ability to wear clothes for oneself should be regarded as the difference between humans and animals. Maybe humans have completely separated from ape-men and embarked on a higher level of evolution since they wore clothes. In some cases, modern humans wear clothes to hide their shame. In fact, they also wear clothes to protect themselves from the sun in the summer and to keep out the cold in the winter. Primates are all hairy, but apes could only rely on hair to play the same role at that time. Over time, clothing gradually replaced the role of hair. The body hair becomes thinner and finer, and the true color of the skin becomes more and more exposed, until most of the hair on the human body has become fine hair.

In this sense, the degradation of human body hair is actually in line with the principle of use it or lose it in Darwin's theory of evolution. Humans are losing less and less body hair in the process of evolution. After the apes of ancient times parted ways with modern humans on the evolutionary path, they did not embark on the path of intelligent creatures. At best, they can only be regarded as primates. They still don't know how to drill wood to make fire, and they don't know what clothes are. So hair is still a camouflage weapon and cold protection weapon for them. Thanks for the invitation! Why is it that only humans have evolved body hair? Other primates have retained this topic. In my personal opinion, the main reason is that humans invented clothes, which replaced the function of body hair. Why do you say this?

Because the original body hair of the human body has the function of protecting the skin and keeping warm from the cold. Since humans invented clothes, it can completely replace the function of body hair. In view of the evolutionary principle of use it or lose it, The body hair that has been replaced by clothes does not have its function and will naturally gradually degenerate. Over time, the body hair on human skin is basically degraded.

The invention of human clothes can not only replace body hair to protect the skin and keep warm from cold, but also add beauty to the appearance of the human body; colorful and diverse outerwear; protect privacy; and make the human skin Become more radiant and eye-catching; become more sexy and touching; promote human civilization life and other functions.

As for other primates, since there was no invention of clothing, their body hair functions have always been used, so their body hair can be preserved. To understand why humans lost body hair during evolution, we first need to know when humans lost body hair. In fact, it is not so easy to determine when humans lost their body hair. This is because almost all fossils are skeletons without skin. This means that we cannot look for evidence directly from fossils. You might think that finding needles, fabrics, etc. during the research process can also directly prove when humans shed their body hair. After all, clothes are only needed by people who shed their body hair. In theory, this idea is good, but in fact, when humans first shed their body hair, most of the "clothes" they used were plant fibers and animal furs, both of which are very easy to decompose. We can no longer find the earliest clothes to determine when humans lost their body hair. In 1999, molecular biologist Mark Stocking found a research method from a text message sent from his son's school. This text message said that two children in the school had lice and hoped that parents would pay attention to hygiene. Mark Stocking immediately realized that he could start with lice to study when humans lost their body hair. We know that lice are a parasite on humans, and they can only live in places with hair and cannot survive in places without hair. Before humans shed their body hair, lice should be crawling along the hair all over the body. When humans shed their body hair, lice can only leave the head and pubic area. Since the body has no hair, the two types of lice cannot communicate genetically through the smooth body. Over time, two different types of lice have been formed, namely: body lice and pubic lice. louse. According to the molecular clock measurement method of lice, we only need to know how many base pairs are different between body lice and pubic lice, and then calculate the speed at which the body louse replicates itself, and how many base pairs there are for each self-replication. , you can find out when the two separated. From this perspective, humans have shed their body hair at least 1.14 million years ago. 1.14 million years ago, humans had not yet left Africa, but they had learned to use fire. This means that even if humans lose their body hair, they can still use fire to keep warm on cold nights, so humans will not become extinct due to the cold. As for why humans lose body hair, the currently most accepted hypothesis is: the heat dissipation theory. We know that after humans walked upright, they were not very fast, and they did not use complex tools to hunt food at that time. They could only make a living by collecting plants, scavenging, and eating meat. However, plants and carrion do not appear in the same place every day. Humans have to spend a lot of time looking for edible plants and following herbivore populations in an attempt to get a piece of the pie from other carnivores.

Occasionally, humans will hunt, but the way humans hunt is most likely to run a marathon, exhaust the opponent to death, and then carry them home. In other words, humans in ancient times had to spend a lot of time walking every day in order to find food. According to research by scientists, humans are the marathon champions of the animal kingdom. The reason for this is probably due to the fact that humans have lost their body hair. We know that after humans shed their body hair, their entire body can dissipate heat and cool down quickly. Other animals do not dissipate heat as quickly as humans, so they cannot run for a long time. For example: Although the leopard's speed is fast, its duration is short. Tigers and lions often hide under the shade of trees and in waterholes during the hot midday hours, rather than coming out to hunt. After humans shed their body hair, they can avoid large predators and obtain food. So the gene was preserved. In addition to the heat dissipation hypothesis, there is also the parasite hypothesis. There are many kinds of parasites hidden in the thick hair, and these parasites can in turn affect human sexual choices. We know that most organisms with parasites on their bodies are unhealthy; while organisms without parasites represent healthy bodies. In ancient times, when humans reproduced, they tended to select individuals with less body hair and fewer parasites, so that human body hair decreased with human sexual selection until it is what it is today. In fact, evolution has no direction, and if humans are allowed to evolve again, perhaps humans will evolve into other different creatures. Furthermore, primates do not use fire. Even if some individuals lose their individuality during evolution, they may become extinct due to cold when the weather gets cold. In fact, there are naked apes in zoos, but this ape is the result of inbreeding and is easily eliminated in nature. Moreover, the main food of most primates is vegetation and fruits on trees, and they do not need to run for a long time, so the cooling system is not only not beneficial to them, but may make them endure the cold. Therefore, the phenomenon of humans losing body hair does not appear in other primates. The species we see now, including us humans, have evolved through a long evolutionary process. In constant struggle with natural conditions, each species has evolved stronger survival capabilities. Human beings are significantly different from other species in this evolutionary process. Not to mention that humans have unique intelligence that enables them to surpass all animals. In terms of appearance alone, humans are also very different from other animals. The most distinctive feature of human appearance is the lack of thick body hair. On the other hand, the other primate brothers are all fluffy. This is a very interesting thing. If you want to know why humans are so special, you must start with the unique characteristics of humans. Let’s put aside the intelligence factor. In addition to intelligence, what unique advantages do humans have compared to other animals? There is one thing, that is, the body fat rate of humans is significantly higher than that of other animals, and humans accumulate fat at the fastest rate among all animals. The livestock we raise for food cannot compare with us at this point, so it’s no wonder it’s so difficult to lose weight. So what is the use of this characteristic of humans? It's very useful, it gives humans the ability to run continuously. We all know that cheetahs can run fast and antelopes can run longer, but compared to humans, antelopes pale into insignificance. Human beings' ability to run continuously far exceeds that of any other animal. It is precisely because humans have strong continuous running capabilities that they can exhaust their prey through long-term tracking and running, and finally capture it. Of course, humans no longer use this ability to hunt. We can only experience this unique feature of humans in marathon races. However, continuous running will lead to electrolyte imbalance, so humans need to supplement salt. With salt, they must perspire, and thick body hair becomes an obstacle to perspiration. In order to better utilize this unique feature of humans, our Our ancestors gradually lost their body hair during evolution. By being able to perspire smoothly, humans can run longer and catch more prey, ensuring the continued development of the human race. We cannot simply use Darwin’s theory of evolution to judge here. The first thing I want to say is that compared with other primates, the first difference in appearance between humans and other primates is that their body hair has degenerated. It can be said that this is not simply caused by evolution, but a mutation.

This mutation, in the environment at that time, did not lead to the extinction of humans. On the contrary, due to the lack of body hair, humans will naturally use some methods that are more beneficial to survival, such as using tools. Compared with other primates, they need more It needs foreign objects to increase its survivability. This is the driving force of evolution. Walking upright is also one of the things that makes humans different from other primates. This should also be considered to be caused by mutation. Later, it will involve a process of survival of the fittest. Human beings gradually adapted to walking upright, learned to use tools more flexibly, invented and created tools, learned to use fire, and finally stood at the top of the earth's food chain. What’s more, use it or lose it, it goes against the law of evolution. Just think about it, I already have enough things to keep out the cold, why would I invent clothes? It is the lack of it that leads to such an invention. Fire not only provided cooked food for the ancient apes to obtain more energy, but also brought them warmth, which is also a main reason why humans are hairless. There is every reason to imagine that the primitive hairy apes gradually felt that thick and long hair was no longer indispensable in their life with fire, and even became a burden, because in the process of obtaining food, they They can exercise without feeling cold, and after calming down, they can rely on fire to resist the cold. They no longer need to wear fur to keep out the cold. But this alone was not enough to make the hominid give up their natural body hair. It was another reason that finally caused the ancient apes to lose their long hair. That is determined by the essential reasons of life evolution. We know that mammals are homeothermic. This is a higher-level function acquired during the long-term evolution process and is the result of adapting to the environment. To maintain a constant body temperature requires them to find ways to eliminate when the ambient temperature is too high. Excess heat in the body. Warm-blooded animals can dissipate heat through their skin. The skin dissipates heat through radiation, conduction, convection, and evaporation. When the skin temperature is close to or equal to the ambient temperature, the first three heat dissipation methods are ineffective. At this time, the evaporation of sweat and water becomes the only way to dissipate heat. With the help of fire, humans gain more energy from their bodies by eating cooked food (compared to other raw-eating primates). The final and most common product of energy, "heat," is much more than that of other mammals. This in turn will cause the body temperature to be too high, and too high a temperature will cause the failure of catalytic enzymes and lead to metabolic disorders. Therefore, a more advanced heat dissipation method than other mammals must be used to maintain a constant body temperature. This more advanced way of dissipating heat is through sweating. Sweating is the main way for animals with sweat glands to dissipate heat in hot environments. Sweat glands are divided into two types: eccrine sweat glands and apocrine sweat glands. They are unique body temperature regulation organs of mammals. Among them, the apocrine glands are scattered along the body hair of animals, while in humans they are less developed and are distributed at the junction of the limbs and are controlled by adrenergic fibers. The apocrine sweat glands of animals generally only secrete a small amount of thick liquid, which emits a special smell. This smell has certain significance in animals' social life and sexual activities. Only a few animals, such as cows and horses, have apocrine glands related to body temperature regulation. After high temperatures and strenuous exercise, the secretion of apocrine glands increases significantly, which helps dissipate heat. Eccrine sweat glands are located at the end of the limbs of mammals, and only in primates, such sweat glands are found on hairy skin. From a functional point of view, although the hairy skin of primates other than humans has eccrine glands, they have no obvious function. The skin of apes is also not moist in high temperature environments. The sweat secreted by eccrine sweat glands is the main source of human sweat. The main component of this sweat is water, and compared to blood, sweat is a hypotonic liquid. When the ambient temperature reaches close to the skin temperature, the eccrine glands begin to secrete sweat. As the water in sweat evaporates on the body surface, a large amount of heat can be lost. At this time, the secretion of sweat and the evaporation of water in it are the only ways for the human body to dissipate heat. It can be seen that human eccrine sweat glands are a unique functional structure newly developed by humans. Through the above discussion, we can assume that (since I am an amateur science enthusiast, all my opinions can only be assumptions) the body hair of ancient humans, like other warm-blooded animals, was to keep out the cold. However, due to eating cooked food The body gained more energy, humans were able to evolve, and the structure subsequently changed in the direction of higher energy utilization, ultimately producing more heat energy. Compared with other animals, the function of body hair to keep out the cold is no longer important, especially for Due to the development of intelligence, humans learned to use tools to use animal fur as clothing to keep out the cold.

On the other hand, in a hot environment, excessive heat in the human body needs to be dissipated quickly, and long body hair hinders the efficiency of water dissipation. If the body hair does not fall away at this time, the temperature in the human body will be higher than normal. level, thus leading to disorders of various physiological functions of the human body, and human evolution cannot be completed. Eventually, the long body hair degenerates into short vellus hair and loses its physiological function of protecting against cold. However, as Darwin said: "The loss of body hair would be inconvenient and probably harmful to man, even in hot climates, since he would be exposed to the scorching heat of the sun and sudden cold." Especially in rainy weather. "How do humans solve this problem? They developed another structure, subcutaneous fat, to resist the cold. This is also a major feature that distinguishes humans from other primates. This feature was once used as evidence that humans originated in the ocean. In fact, the development of subcutaneous fat is to compensate for the reduction in cold resistance caused by the loss of body hair in humans. It is a structure that was developed during the long process of apes evolving into humans, so it is not found in other primates. This hypothesis may also explain the existence of hair on the head and the hair on the joints of the limbs. The hair on the head is kept just to keep out the cold. Due to evolutionary reasons, the human brain gradually increases. However, an overly large brain will cause a series of problems, such as difficulties at birth. This requires the head to save space as much as possible to accommodate the rapid development of the brain. and increase (also due to fire), so there is almost no subcutaneous fat on the head to resist the cold. (This may also be the case in other primates. The increase in human cerebral cortex folds cleverly increases the area while Not increasing the size is also to save space) So, naturally, the hair on the head is preserved to keep out the cold. As for the reason why the hair at the junction of the limbs is preserved, I think it is this; since the junction of the limbs has almost no contact with the outside world, the function of dissipating heat has little effect there, so the body hair there is preserved. The process of humans losing body hair is a very long process. In a long enough evolutionary process, the gradual disappearance of body hair will clear the way for humans to improve energy utilization, and the improvement in energy utilization will allow a branch of ancient apes to complete the evolution. Eventually becoming human, this process still follows the basic principle of natural selection. It was nature that selected a group of ancient apes whose body hair gradually disappeared. It was fire that brought warmth to the ancient apes and illuminated their path of evolution. Heresies [cover face] [cover face] The degeneration of hair is because it is afraid that people will burn it when people use fire. Once scared, the hair will not be happy [laughing and crying] [laughing and crying]