The story of the human body: evolution, health and disease
author
(America) Daniel. Lieberman
translator
Cai Xiaofeng
Two halves of beans
/Books/Themes /27052052/
catalogue
order
Introduction What does adaptation mean?
How does natural selection work?
Difficult concept of evolutionary adaptation
Why is the history of human evolution important?
Why is evolution important now and in the future?
The first part is the five stages of human evolution.
0 1 Homo erectus
02 Australopithecus australis
The earliest hunter-gatherers.
04 ancient humans in the ice age
Homo sapiens with cultural creativity
Part II Agricultural Revolution and Industrial Revolution
06 progress, mismatch, bad evolution
07 paradise lost
08 body crossing
Part III Present and Future
A vicious circle of excess energy.
10 use, enter, waste and return
1 1 The hidden trouble behind novelty and comfort
Conclusion Using evolutionary logic to create a healthy and bright future for mankind.
End of movement
"It is important to plant our garden."
Translator's postscript
We are used to paying more attention to the short-term cost-benefit rather than the future cost-benefit Economists call this behavior hyperbolic discount, which makes us more rational when dealing with long-term goals, but less rational when dealing with our immediate desires, behaviors and pleasures. Therefore, we can tolerate potentially harmful things and even find pleasure in them, because the improvement they bring to our lives now exceeds our judgment on their ultimate cost or risk.
I think there are other deeper evolutionary explanations to explain why humans sometimes do novel things that are potentially harmful. The most important thing is that we don't think many novel behaviors are harmful, because we don't think they are novel, and we are willing to regard the world around us as normal psychologically, so it is also benign.
Forming a habit is a habit in itself, and questioning all your actions may lead to great pain. Therefore, although rational people should or can question their own behavior or environment, I will not do so. History tells us that ordinary people can get used to unimaginable terrible behavior under normal circumstances, which is also what philosopher Hannah Arenoff called "the evil of mediocrity". Evolutionary logic shows that when unhealthy novel behaviors and similar aspects appear frequently in our environment, people will feel used to it.
It is normal to accept the world around us, and this inherent tendency of human beings may have potential negative effects, which will lead to mismatch and poor evolution in unexpected ways.
The second evolutionary explanation for why people often do something novel but potentially harmful is that we often mistake comfort for happiness. Some abnormal but comfortable things in daily life are really novel, but they may be harmful to health. There are many examples of this.
Apart from fashion considerations, the most important function of shoes is to protect your soles. There is no doubt that the protective performance of soles is better than calluses, but the disadvantage of platform shoes is that it will limit the sensory perception.
Of all the foot pads in shoes, the heel plays the most important role. Heel is the first part of the body to land when walking, especially the heel of shoes, and sometimes it is the same when running. This kind of collision will quickly form a peak force on the ground, which is called peak impact force.
Figure Influence of walking and running on the ground (barefoot and wearing shoes)
As can be seen from the figure, when people walk, they usually follow the ground with their feet, which will produce a small peak impact. When running barefoot, the peak impact force produced by the heel is much larger and faster. However, in the running state, cushioning shoes can greatly slow down the speed at which the impact force reaches the peak, and the forefoot landing (wearing shoes or barefoot) will not produce the impact force peak.
Because pain is an evolutionary adaptation to avoid harmful behaviors, it is no wonder that many people who have experienced barefoot running or wearing thin-soled shoes often land on the forefoot or the middle of the sole when running long distances on hard or uneven roads, while many people who are used to wearing running shoes and usually follow the ground with their feet will land on the forefoot when asked to run barefoot on hard roads.
The design of shoes also includes other functions to increase comfort, which will also affect your body.
Arch pads and hard curved soles undoubtedly bring comfort, but they may also cause some problems. One of the most common is flat feet. Studies have compared people who are used to barefoot with those who wear shoes, and found that barefoot people have almost no flat feet, and their arch shapes are much the same, neither high nor low. Flat feet are an evolutionary mismatch.
Another common problem related to wearing shoes is plantar fasciitis. Plantar fascia is a layer of tendinous tissue on the sole of the foot, which can straighten the arch of the foot together with muscles. There are many reasons for plantar fasciitis, but one mechanism of this disease is that the muscles of the arch become weak and cannot maintain the shape of the arch. Fascia must compensate these weak muscles. Fascia is not very suitable for high pressure, so it will be inflamed and painful.
Other functions of shoes can also lead to mismatch.
In short, our adaptation to barefoot in the process of evolution is the reason why many people suffer from foot disease. The shoes with the simplest structure have existed for thousands of years, but some modern footwear designs may seriously interfere with the natural function of the feet to achieve the purpose of comfort and fashion. Faced with these mismatches, more and more footwear consumers began to wear shoes with the simplest structure, no heels, hard soles, arch pads and no tips.
The evidence that myopia is a modern disease is reasonable, because myopia is likely to be a serious disadvantage until recently.
Myopia is a complex trait, which is caused by the interaction of many genes and many environmental factors. However, because human genes have not changed much in the past few centuries, the prevalence of myopia in the world in recent times is bound to be mainly due to environmental changes. Among all the identified factors, the most common culprit is working at close range: focusing on nearby images for a long time, such as sewing, reading books or words on the screen.
Imagine how your eyes focus on distant objects.
In normal eyes, light first reaches the cornea, then is refracted by the lens (which can be relaxed by the contraction of the ciliary muscle) and focuses on the back of the retina. In myopia, the refractive distance (below) is too long, resulting in the focus of distant objects not reaching the retina.
The hypothesis of close work is controversial and has never been directly verified in humans. Other animal experiments show that abnormal visual input can lead to myopia, which, like close work, cannot be explained by the close work hypothesis. All kinds of evidence lead to a hypothesis: normal eyes need a variety of mixed visual stimuli, such as multiple intensities of light and different colors, rather than the monotonous and dim colors of indoor environment or pages.
We still have a lot to know about myopia, but two basic facts are already clear. First of all, myopia was a rare evolutionary mismatch in the past, but it is getting worse in the modern environment. Secondly, even though we don't fully understand what causes children's eyeballs to grow too long, we know how to effectively treat the symptoms of myopia with glasses.
We still have a lot to know about myopia, but why people are nearsighted, how to become nearsighted, and how to help nearsighted people highlight some typical characteristics of poor evolution. First of all, like many evolutionary mismatches, myopia is passed from parents to their children in a non-Darwinian way without their knowledge. Although some genes may make some children prone to myopia, the primary factor that causes myopia or is passed on from parents to children is the environment, and even glasses may sometimes make the problem worse. Secondly, we may have enough knowledge to prevent myopia, but so far, the prevention of myopia has received little attention.
One problem caused by sitting in a comfortable seat for a long time is muscle atrophy, especially it is difficult to maintain the core muscles of the back and abdomen responsible for maintaining the stability of the trunk. As far as muscle activity is concerned, there is not much difference between sitting in a chair and lying in bed. Another atrophy caused by sedentary is muscle shortening.
If we consider the cross-cultural model of low back pain and the understanding of the evolution of back function, there will be clues that low back pain is an evolutionary mismatch to some extent, although there are many reasons. The key issue to consider is that, from an evolutionary point of view, so far, no one studied has used their backs in a normal way. In other words, hunter-gatherers use their backs moderately. The intensity is neither as high as subsistence farmers nor as gentle as sedentary office workers.
Relationship model between physical activity level and back injury
People with extremely low and extremely high levels of physical activity have a higher risk of injury, but the reasons are different.
In short, there may be a balance between the way you use your back and the health of your back. The normal back is not favored by chairs, but it is used to varying degrees all day, even when sleeping, but the intensity is in the middle range. Entering an agricultural society may be bad news for mankind. With comfortable chairs, shopping carts, suitcases, elevators and thousands of labor-saving devices, now we are facing the opposite problem.
Since the Paleolithic Age, mankind has made a surprising number of innovative inventions, creating novel stimuli for the human body. Compared with such a large number of inventions, those machines that improve comfort are of course just the tip of the iceberg. Just as natural selection can eliminate harmful mutations and promote adaptation, cultural evolution will eventually screen out better innovations and eliminate those that are not so useful or even harmful.
However, the operating standard of cultural selection is not always the same as that of natural selection. Natural selection only selects new mutations that are conducive to improving the survival and reproductive ability of organisms, while cultural selection may only promote new behaviors because they are popular and profitable, or because of other favorable factors. They can bring a lot of benefits and fun, but they can also cause evolutionary mismatch, which easily conforms to the characteristics of poor evolution.
Recognizing that many innovations, including those specially designed for comfort and convenience, are not always beneficial to human health does not mean that we need to avoid all new products and technologies. However, from an evolutionary point of view, the human body can tell us that some novel products may lead to evolutionary mismatch. Millions of years of evolution have failed to adapt our bodies to many modern technologies, at least in quantity or degree.
For the diseases brought by novelty and comfort, the solution is not to lose the convenience brought by these modern technologies, but to treat both the symptoms and the root causes and prevent the cycle of bad evolution.
Since the agricultural era, natural selection has not stopped, but has continued until today, enabling people to adapt to changes in diet, bacteria and environment. However, the speed and intensity of cultural evolution greatly exceed natural selection, and the body we inherited is still largely adapted to the various environmental conditions that we have evolved for millions of years.
The end result of this evolution is that we have become a biped with large brain capacity and moderate fat, which can reproduce relatively quickly, but it takes a long time to mature. We are also adapted to engaging in endurance physical activities, such as walking and running for long distances, climbing, digging and loading things. We evolved to eat a variety of diets, including fruits, tubers, game, seeds, nuts, and other foods with high sugar, simple carbohydrates, low salt and high protein, complex carbohydrates, cellulose and vitamins. Humans are also incredibly adapted to manufacturing and using tools, effective communication, close cooperation, continuous innovation and using culture to meet various challenges. These extraordinary cultural abilities made Homo sapiens spread to the whole earth quickly, and then stopped hunting and gathering very paradoxically.
The main exchange price between the new environment we create and the body we inherit is mismatch disease. Adaptation is a subtle concept. No environment is particularly suitable for the human body, but the biological mechanism of the human body can not fully adapt to living in a permanent settlement with high population density and human pollution. We haven't fully adapted to being too relaxed, eating too much, being too comfortable, being too clean and so on. Although we have made great progress in medicine and health recently, there are still too many people suffering from many diseases that were rare or unknown in the past. Among these diseases, there are more and more chronic non-communicable diseases, many of which are caused by the progress of civilization exceeding the adaptability of human body.
What we are facing now is a contradictory situation: the human body is getting better and better in many aspects, but worse and worse in other aspects. To understand this paradox and the corresponding countermeasures, we need to consider two related processes from the perspective of evolution. The first process has been summarized above, that is, the ever-changing environment makes us more and more vulnerable to various diseases caused by evolutionary mismatch. Understanding the causes of mismatch is very important for finding out the prevention and treatment methods, which highlights the importance of the second process: the vicious feedback cycle of poor evolution. Although many mismatched diseases can be prevented, we often cannot solve their pathogenic environmental factors. When we pass on the same pathogenic environmental conditions to future generations through culture, the disease will continue to spread and even worsen.
To this day, natural selection continues. This is because natural selection is basically the inevitable result of two phenomena, which still exist today: genetic variation and the difference in reproductive success rate. Just as natural selection is bound to affect some people with low immunity to infectious diseases, there are bound to be some people who are genetically difficult to adapt to today's environment with abundant materials and insufficient physical activity.
The evolution of human beings is not over, but unless there are major changes, it is very unlikely that natural selection will adapt our species to common mismatched non-communicable diseases in a dramatic and significant way. One reason is that many of these diseases have little or no effect on fertility. For example, patients with type 2 diabetes usually suffer from type 2 diabetes after delivery, and even after the onset, it can still be well controlled for many years. Another reason is that natural selection can only affect the success rate of reproduction, which can be passed from father to offspring through heredity. Some obesity-related diseases may affect reproductive function, but these problems are influenced by strong environmental factors. Finally, although culture sometimes stimulates natural selection, it also has a powerful buffering effect. Every year, a large number of new products and treatments are developed to enable patients with common mismatch diseases to better cope with their symptoms. No matter how natural selection works, its speed is too slow to be measured in our lifetime.
It may be a dangerous sci-fi plot to cure complex diseases quickly, but the development of modern medicine for decades has also brought countless beneficial treatments to mismatched diseases, which can save lives and alleviate pain. There is no doubt that we must continue to invest in basic biomedical research to promote its further progress, but I expect this progress will be slow and gradual. Most of the drugs available at present have limited effects and are accompanied by adverse side effects; In the treatment of non-communicable diseases, only a few can provide real cure, and most can only relieve symptoms or reduce the risk of death or illness.
Another reason why I don't expect a major biomedical breakthrough in chronic mismatch diseases in the near future, especially those unrelated to pathogens, is that the etiology of these diseases is not easy to focus effectively. We can't expect medical science to design some very effective treatments to cure most non-infectious mismatch diseases. There is also a hidden dilemma. Many of these diseases can be prevented to a certain extent through environmental changes and behavior changes, and sometimes to a great extent, but the former is difficult to implement and the latter is difficult to adhere to. Good traditional diet and exercise are not a panacea to revive the dead, but dozens of studies have clearly proved that they can greatly reduce the incidence of the most common mismatch diseases.
Prevention is indeed a good medicine, but human beings always lack political or psychological determination and the determination to take preventive action for our own best interests. Fundamentally speaking, prevention is a better and more cost-effective way to promote health and longevity.
The cornerstone of public health work is to design methods to educate people and empower them, so that they can better use and take care of their bodies and make more reasonable decisions.
The reasons why people take irrational behaviors on health issues are increasingly becoming the theme of innovative research. A large number of experiments have proved that human behavior is beyond our conscious control in many aspects. Our reaction comes from instinct. These quick judgments are often common, repetitive and instantaneous decisions, such as choosing chocolate cake or celery, climbing stairs or taking the elevator. Although slow and careful thinking can restrain these instincts, it is very difficult to transcend this behavior. These and other unhealthy instincts may be conducive to increasing the chances of survival and breeding more offspring in the era of material scarcity, but in the environment of material abundance in recent times, they have only become negative adaptations. In other words, we have been making irrational decisions, but it is not our own fault.
I think the evolutionary perspective can provide a useful framework on the basis of two principles. First, because all diseases are caused by the interaction between genes and environment, we can't redesign our genes, so the most effective way to prevent mismatched diseases is to rebuild our environment. Second, the human body has experienced millions of generations of evolutionary adaptation in Darwin's so-called "competition for survival", and the conditions at that time were very different from those now. Before modern times, human beings had no choice but to act in a way determined by natural selection. Our ancestors are usually forced to eat a natural and healthy diet, get enough physical activity and sleep, have no chairs to sit on, and rarely live in crowded, dirty permanent settlements that are easy to spread infectious diseases. Therefore, evolution has not always allowed human beings to choose healthy behavior, and human behavior is forced by nature. In other words, the evolutionary point of view reminds us that human beings sometimes need external forces to help themselves.
According to the spirit of "moderate paternalism", it is wiser and fairer to formulate laws and regulations to help people make reasonable judgments and choices according to their immediate interests.
Some people mistakenly think that natural selection means "survival of the fittest". This statement was created by Herbert Spencer in 1864, but Darwin never used this statement and he will not use it. Because about natural selection, it is better to say "survival of the fittest." Natural selection cannot create perfection; Only those unfortunate individuals who are less adaptable than others will be eliminated.
From a macro perspective, if there is one of the most revolutionary adaptations in human evolution, it must be our ability to evolve through culture rather than just natural selection. Today, cultural evolution is surpassing natural selection in speed, and sometimes even more exquisite than natural selection.
Just as cultural innovation has caused many mismatched diseases, other cultural innovations can also help us prevent these diseases. This method needs to combine science, education and rational collective action.