It is difficult to reproduce without mistakes. It is inevitable that there will be some mistakes in the process of gene replication. These wrong genes sometimes make organisms more adaptable to the environment, which will be passed down from generation to generation. The more you breed, the more mistakes you make. This process has been repeated again and again for billions of years. Finally, Homo sapiens stepped onto the stage of history. But the story is not over yet. Evolution will not stop here, and the speed of our evolution may even be much faster than ever before.
It is difficult for us to predict what will happen in the future. The world may change in a completely unexpected direction, but at least we can make some reasonable guesses. Paradoxically, the best way to predict the future is to look to the past, assuming that the previous development trend will continue in the future. According to this line of thinking, we have come to some rather surprising conclusions.
We may live longer, be taller and be lighter. We may become less aggressive, but the size of our brains will also decrease. We will become happy and friendly all day like golden retrievers, but this is not a good thing. In any case, this is at least a possibility we face in the future. But to understand why all this happened, we must start from biology.
The new environment we create forces us to adapt.
The end of natural selection?
Some scientists believe that the rise of civilization means the end of natural selection. It is true that most of the pressure of choice in the past has disappeared, such as predatory animals, famine, plague, war and so on.
Thanks to high-yield crops, fertilizers and family planning measures, famine has almost disappeared now. Violence and wars are far less frequent than in the past. Although the modern army has nuclear weapons, perhaps nuclear weapons are precisely the reason for the reduction of wars. The lions, wolves and saber-toothed tigers that once killed us in the dark are now either endangered or extinct. The plagues that killed millions of people (smallpox, Black Death, cholera, etc.) have also been put to rest with the blessing of vaccines, antibiotics and clean water.
But evolution has not stopped, but the driving force has changed. Now evolution is no longer "survival of the fittest", but "reproduction of the fittest". Although nature no longer poses a threat to our lives, we still need to find partners and have children, so "sexual selection" now plays a more important role than "natural selection" in human evolution.
In addition, although nature no longer controls our evolution, the unnatural environment we have created has created new pressure of choice, such as culture, technology, cities and so on, which are completely different from the situation faced by human beings in the Ice Age. But we have not adapted well to this new world, so we need to further adjust our adaptation.
This process has already begun. After humans began to eat cereals and dairy products, they gradually evolved genes that helped to digest starch and milk. Cities provide an environment for diseases to spread easily, so genes begin to mutate in the direction of disease resistance. Besides, for some reasons, our brains have become smaller. The unnatural environment thus creates unnatural selection.
In order to predict the next development direction, we should also look to prehistoric times and analyze the evolution trend in the past 6 million years. Some will continue, especially after the birth of agriculture and civilization in the past 10 thousand years.
We are now facing some new pressure of choice, such as the decreasing mortality rate. In this regard, history can provide us with limited information. However, we can observe how other species react when faced with similar pressures, especially domestic animals. After all, there is a saying that human beings are becoming a domestic "ape", but the keeper is human beings.
Leonardo da Vinci's Vitruvian Man is based on the perfect human body in his mind, but his view of "perfection" may become completely different in the future.
life
It is almost certain that human life will be longer and longer, and it will be much longer than today's level. The life cycle will change with the death rate. When the death rate is high, the reproductive age of animals will be reduced, or reproduction will stop completely. In this case, it is meaningless to evolve anti-aging or anti-cancer genes, because there is no time to use them.
When the mortality rate is low, the situation is just the opposite. You will have plenty of time and don't need to rush to sexual maturity. The body will also adjust to the direction of prolonging life span and increasing fertility rate, giving you more time to reproduce. Therefore, animals with fewer natural enemies (such as those living on islands or in the deep sea, or larger ones) tend to live longer. Greenland sharks, tortoises and arctic right whales are such examples. They reach sexual maturity later and can live for hundreds of years.
Even before the birth of civilization, human beings have been a special existence among apes, because the mortality rate is lower and the life span is longer. Spears and bows and arrows can help humans resist predators, and sharing food with others can avoid starvation. Therefore, the sexual maturity of human beings is getting later and later, and the life expectancy is getting longer and longer, up to 70 years old.
However, in ancient times, the mortality rate of children was always high. The probability of dying before 15 years old could reach 50% or even higher, and the average life expectancy was only 35 years old. Even after the rise of civilization, the child mortality rate has remained high. In the19th century, the average life expectancy of human beings was shortened to about 30 years due to plague and famine.
However, in the past two centuries, with the improvement of nutritional conditions, the invention of new drugs and the improvement of health awareness, the mortality rate of adolescents in most developed countries has dropped below 1%. The average life expectancy in the world has increased to 70 years, and it is as high as 80 years in developed countries. The increase of life span is mainly related to the improvement of health status, and has little to do with evolution itself, but it has laid a good foundation for evolution to further prolong human life span.
Nowadays, there is almost no need for us to have children early. Even if there is, I have to wait until I finish my studies. As the life span doubles, we have to adjust and adapt to it. Nowadays, more and more people live to be 100 years old, even 1 10 years old. Maybe our genes will continue to evolve in this direction until the average life expectancy of human beings reaches 100 years old or above.
Body shape and strength
Animals generally evolve into larger and larger bodies. We have observed this trend in Tyrannosaurus Rex, whales, horses and primates, and Terran is no exception.
Early Terrans, such as Australopithecus afarensis and Early Terrans of Homo habilis, were petite and only 120 to 150 cm tall. The later Homo erectus, Neanderthals and Homo sapiens were all taller. Since the beginning of historical records, human height has been increasing, which is related to the improvement of nutritional conditions to some extent, but the evolution of genes seems to be one of the influencing factors.
However, we still don't know why people are getting bigger and bigger. The mortality rate may promote the evolution of body shape to some extent, because the growth of the body takes time; The longer the life span, the longer the growth time. In addition, human women are also more inclined to choose tall men. These two reasons may have contributed to the continuous growth of human height. Today, the height of Europeans ranks first in the world, especially in the Netherlands: the average height of men is 183cm, and that of women is 170cm. One day, most people can reach or even exceed this level.
As we grow taller, our bodies will become more and more slender. Over the past two million years, as our dependence on brute force decreased and our dependence on tools and weapons increased, the texture of bones became lighter and lighter. Agricultural civilization makes it unnecessary for us to run around, and the sedentary time at home is greatly increased, resulting in lower and lower bone density. Nowadays, we are either sitting at the desk typing or driving, so this trend may continue.
Compared with other apes, human muscle mass is gradually decreasing, especially in the upper limbs. Our ancestors were able to slaughter antelopes, dig roots and plow fields. Modern work is more mental work than manual work. Even for manual workers such as farmers, fishermen and loggers, tractors, hydraulic devices and chain saws have taken away a large part of the pressure. As the necessity of physical strength becomes lower and lower, our muscles will become smaller and smaller.
Our jaws and teeth have also become smaller. Early plant-eating terrans all had huge molars and mandibles, which were used to grind fiber-rich plants. But after we started eating meat, with the appearance of cooking behavior, our jaws and teeth began to shrink. Modern refined foods such as chicken nuggets and ice cream hardly need to be chewed, so the volume of the lower jaw will continue to decrease and wisdom teeth may disappear in the future.
Dogs have become a highly diverse species under the care of human beings. After mankind/kloc-walked out of Africa 0/0 million years ago, different tribes were separated by deserts, oceans, mountains, glaciers and long distances. In different parts of the world, people are faced with different choice pressures, such as different climate, lifestyle and aesthetic standards. All these have led to the development of our looks in different directions, and gradually evolved different skin color, eyes, hair and facial features.
With the rise of civilization and the emergence of new technologies, these people are reconnected. War, imperial expansion, colonization and trade (including human trafficking) provide opportunities for different races to intermarry, and human beings are constantly changing. Today, roads, rails and airplanes connect the world's population closely. Bushmen, an African aborigine, can walk sixty or seventy kilometers in order to find a partner; For us, it is not difficult to cross the sea. We are becoming more and more cosmopolitan and can "mix and match" with people of other races at will. In the future, there will be more and more mixed races in the world, such as light brown skin, black hair, African-European-Australian-American-Asian descent, and the skin color and facial features of people in the future will gradually develop to the global average.
Sexual selection will further accelerate the evolution of appearance. Although most forms of natural selection have failed for human beings, they still play an important role in the choice of spouses. Humans may become more attractive in the future, but their looks will gradually become consistent. Global media will also create more uniform aesthetic standards, so that all human beings pursue the same "ideal type." However, if the ideal type of human beings becomes more masculine men and more feminine women, the gender difference may widen further.
IQ and personality
Finally, the brain and thinking, the most remarkable characteristics of our human beings, will also evolve, and the changes may not be small. In the past 6 million years, the size of the brain of the Terran has almost tripled, indicating that natural selection tends to have a larger brain driven by the use of tools, complex social systems and languages. You may think that this trend will continue, but it is not.
In fact, our brains are shrinking. The brain volume of Europeans reached its maximum at 1 10,000 to 20,000 years ago, just before the invention of agriculture. After that, the brain has been shrinking Our ancient ancestors, even medieval humans, had bigger brains than modern humans, and we still don't know why.
Perhaps it is because, after the establishment of farming civilization, the body's intake of fat and protein has been greatly reduced, leading to the growth of a larger brain has become a "costly" thing. The energy consumption of the brain is quite amazing, and the calories burned every day can account for 20% of the whole body. In an agricultural society where famines are common, a bigger brain may be a burden instead.
Perhaps the life based on hunting and gathering is more brain-intensive than farming in some ways. In a civilized society, you don't need to try to deceive lions and antelopes, and you don't need to remember the location of every fruit tree and every water source within one square kilometer of Fiona Fang. Making and using bows, arrows and spears also requires fine movement control and coordination skills, and also requires mastering the skills of tracking animals. Maybe after we stopped hunting, the brain area responsible for these jobs shrank.
It may also be because there are professional people in large societies who do professional things, so they spend less brain power. People in the Stone Age need to master many skills, such as hunting, tracking, gathering, making herbs, making tools, waging wars, creating music and "magic" and so on. However, modern human beings have fewer things to do, are more specialized, and have a finer division of labor. In a civilized society, we just need to focus on doing one thing and rely on others to do other things.
Having said that, brain size doesn't really determine everything. The brains of elephants and killer whales are bigger than ours, and Einstein's brain is smaller than the average human, but what is the result? Neanderthals are similar to us, but they are mainly used for vision and body control, and there is not much distribution in language and tool use. Therefore, we still don't know what effect the decrease of brain mass will have on the overall intelligence. Maybe when we lose some of our abilities, we will strengthen other abilities that are more related to modern life. It is also possible that we can achieve the same brain processing power with fewer and smaller neurons now.
Interestingly, the brains of domestic animals have also become smaller and smaller in evolution. After being domesticated by humans, the brain mass of sheep decreased by 24%, that of cattle decreased by 26% and that of dogs decreased by 30%. This can't help but make people feel a little uneasy: maybe we, like these livestock, are more and more inclined to follow the crowd and use less brains.
Our personalities will also change. In a hunting and gathering society, human beings need to be aggressive in order to capture large mammals or fight with other tribes. But now, if we want to buy meat, we go to the vegetable market, and if there is any dispute, we go to the police station or the court. Although the war has not completely disappeared, the death rate has dropped to the lowest level in history. Nowadays, aggression has become a feature that is not suitable for human society, and may gradually disappear with evolution.
Changes in social rules will also change human character. The population size of human beings is far larger than that of other apes. In the hunting-gathering era, a tribe can reach as many as 1,000 people. Nowadays, the population of a large city is as many as millions. In the past, interpersonal relationships were relatively simple, and they often lasted for a lifetime. But nowadays, we live in a crowded city and often run around with the change of work. Although many interpersonal relationships have been established, most of them are fleeting, and many times they are just "netizens". The world will force us to become more extroverted, open and tolerant. But in such a vast social network, we may become more and more obedient and blindly follow the crowd.
Not everyone can adapt to this change psychologically. Most of our intuition, desires and fears come from our ancestors in the Stone Age. Their life significance comes from hunting and gathering food for their families, fighting with their neighbors, and praying to the gods in the dark. Modern society meets our material needs well, but as descendants of primitive people, our psychology is still hungry.
Perhaps because of this, more and more people are suffering from psychological problems such as loneliness, anxiety and depression. Many people choose to drown their sorrows in wine. Because people tend to choose partners who are not prone to these psychological problems, our mental health may be improved and the happiness of the whole species will increase. But this result comes at a price. Many great geniuses have a "devil" hidden in their hearts. Leaders such as Lincoln and Churchill, scientists such as Newton and Darwin, artists such as Herman Melville and Emily Dickinson all have to fight against depression. Some people, such as Virginia Woolf, Van Gogh and kurt cobain, committed suicide, while others were ruined by drug abuse for life.
Therefore, while these mental problems are removed from the human gene pool, we may also lose these talented and creative leaders, writers, artists and musicians. Future human beings may be able to adapt better psychologically, but they have lost a lot of interest and are difficult to lead the scientific revolution. In other words, they will become stable, happy and boring.
There used to be nine different human species on the earth, but now only we are left. But is it possible to evolve new human beings in the future? If we want to do this, we need to isolate the population and exert different pressure of choice. Now distance is no longer an obstacle, but in theory, we can achieve reproductive isolation through selective mating. If human beings are strictly isolated in culture, such as intermarriage based on different religions, classes, castes and even political ideas, it is possible to evolve new races and even species in the future.
In H·G· Wells' famous sci-fi novel The Time Machine, different classes have evolved completely different races. The upper class evolved into Eloise, beautiful but useless; The working class has evolved into Molok people, who are ugly and live underground. The latter conquered the Eloi people through the uprising and turned them into their own slaves.
In the past, religions and living habits sometimes formed genetically distinct races, such as Jews and Gypsies. Nowadays, although political ideas can also cause differences, will this difference develop to the genetic level? Liberals tend to associate with other liberals, and conservatives prefer to get along with conservatives, just as leftists don't date Trump fans.
But will these two kinds of people evolve into two different species and hold completely different ideas? Probably not. However, culture does affect our evolutionary direction in many ways. If cultures are in full bloom, human genetic diversity can be preserved, even in by going up one flight of stairs.
Other possibilities
So far, this paper has been taking history as a mirror and predicting the future. But in some ways, the future may be very different from the past, after all, the evolutionary mechanism itself is constantly evolving.
One of the most extreme possibilities is directed evolution, that is, we actively control the evolution direction of human beings. We are actually doing this when we choose a partner according to our favorite appearance and personality. For thousands of years, the ancients have been following the "arranged marriage" to find excellent hunters for their daughters. Even in free love, the man usually needs the consent of the woman's parents. Similar customs are found in many parts of the world. In other words, our children are the result of our own "breeding".
In the future, we may know more about what we are doing and have more control over the genes of future generations. We can now carry out genetic disease screening for ourselves and our embryos, and we may be able to choose embryos with the genes we want in the future, just like crop breeding. The direct editing of human embryo DNA has proved the technical feasibility, but it is still controversial in morality. After all, it is equivalent to turning children into the objects of medical experiments. But if this technology can ensure 100% safety, in the future society, if you don't try to give your child the best genes, you may not be worthy of being a parent.
Computers have also brought us a brand-new choice pressure. Nowadays, there are more and more online dating websites, which is equivalent to entrusting our decision-making power on children's personality and appearance to computer algorithms. Digital codes determine to some extent which genetic codes you will pass on to future generations, just as they affect what content is pushed to the homepage of your shopping website. It sounds like a terrible science fiction novel, but it's already happening. It is difficult for us to predict where we will go next, but it seems unwise to hand over the future of mankind to smartphones, the Internet and the corporate giants behind them.
When discussing human evolution, we usually only look to the past, as if our greatest achievements and the most arduous challenges were all in the distant past. But as technology and culture enter a period of accelerated change, so do our genes. Perhaps the most interesting thing about evolution is not the origin of life, dinosaurs or Neanderthals, but the present and the future. (leaves)