If a disaster leaves only one man and one woman on earth, how long will it take to return to 7.8 billion?

Human beings are the only intelligent life on earth, and they are the advanced animals at the top of the food chain. There are millions of animal species on the earth, and the number of different animal races is different. As a senior animal and the overlord of the earth, human beings naturally have the largest number. According to the current statistics, the number of human beings on the earth has reached 7.8 billion.

Once a friend left a message and raised such an interesting topic: if a disaster left only one man and one woman on the earth, how long will it take for the population to return to 7.8 billion again? I believe there have been a lot of discussions on this issue on the Internet. Different people have given different answers. Some people think it will take at least tens of thousands of years to achieve it. Some people think that it will only take thousands of years to recover, others think it will only take hundreds of years.


So which one is more reliable and accurate? In fact, there is no definite answer to this question, because the speed of population reproduction is affected by many factors. There are factors from nature, and there are also factors from the speed of human development.

We all know that the ancestors of modern human beings were actually African Homo sapiens 250000 years ago. About 70000 years ago, African Homo sapiens went out of Africa and began to spread to all parts of the world. After tens of thousands of years of evolution and development, there is now a rich and colorful human world on earth, with a population of 7.8 billion today. So why do African Homo sapiens of more than 70000 years want to go out of Africa and spread to all parts of the world?

Some people may say that it is because African Homo sapiens have great ideals and want to spread the seeds of human beings all over the world. In fact, this kind of cognition is wrong. Even modern people, I’m afraid not many people have such noble sentiments. And African Homo sapiens are even less likely to have this kind of cognition. The fundamental reason why Homo sapiens left Africa 70000 years ago is survival.


To know that human ancestors can only use simple tools, the requirements for living environment is very high. Why millions of years ago, various kinds of human beings were born in various parts of the earth, and only African Homo sapiens survived in the end? The core reason is that Africa in ancient times was the place with the richest resources and the best environment on earth.

The excellent African grassland and stable African environment enable Homo sapiens to continuously evolve and develop in hundreds of thousands of years. However, we should understand that the ecological environment of the earth will not remain unchanged, and some major changes will often take place. When Homo sapiens first emerged 200000 years ago, the population might have reached 20000.


However, 70000 years ago, a huge eruption of a super volcano led to a large number of global climate upheavals. This is the “Duoba catastrophe”. This ecological upheaval has a great impact on the ecology of Africa. It turns out that there are only about 1000 Homo sapiens left in the tens of thousands of Homo sapiens tribes. After the upheaval, Africa is no longer suitable for Homo sapiens.

In order to survive, Homo sapiens had to go out of the African plain where they had lived for more than 100000 years and began to look for new oasis environment around the world. In this way, African Homo sapiens have gone out. After tens of thousands of years of development, they have spread all over the world, and their population has grown from more than 1000 to 7.8 billion.

If a disaster leaves only one man and one woman on earth, it is not easy to recover to 7.8 billion people. If there is only one man and one woman left in a devastating ecological disaster, then the two of them need to start their development again from the primitive society. If all goes well, after tens of thousands of years of reproduction, the number of human beings is expected to return to 7.8 billion again.


If there is only one man and one woman left in the human race because of the drastic ecological changes, it will not take long for two people to survive to 7.8 billion people depending on the rich resources and good ecological environment. It may only take thousands of years. In the early days, population reproduction was naturally very slow.

However, as time goes on, the speed will be faster and faster. In fact, human civilization only existed for about 5000 years, while 5000 years ago, the world’s population could only be tens of millions. Even before mankind entered the era of industrial revolution, the world’s population was not large, perhaps less than 1 billion.


According to a scientist’s statistics, in 1800, the world’s population was about 1 billion years. From 1800 to 2020, only 220 years have passed, but the population has nearly tripled. The reason why the population has multiplied so fast is mainly due to the welfare brought by science and technology. With the advent of the era of science and technology, human beings are basically no longer hungry. At the same time, medical conditions are constantly improving, and human life expectancy is also increasing significantly.

Of course, if there is only one man and one woman left in the human race, we will have to consider another serious consequence, that is, a series of consequences brought about by inbreeding. Gene is the core of the evolution of life, and the continuous mutation and evolution of gene is the basis of the healthy existence of life.

Inbreeding can not make the gene get better advantage and mutation, it can only make the gene get worse and worse, and make a species perform worse and worse. With the development of biology, human beings are deeply aware of the disadvantages of inbreeding, so this kind of behavior is generally prohibited in modern society.


I believe many friends know that human genes are not perfect. There are many defects in our gene pool. In fact, these defects are the result of the inbreeding of human ancestors. We should know that it is not long since human beings really began to pay attention to inbreeding and prohibit it. It may be only a few hundred years at most.

We should know that in the feudal era of our country, close relative marriage was also a common phenomenon. Only when human beings enter the era of science and technology and have scientific guidance, can they really realize the harm of inbreeding. However, all kinds of harm caused by the long years of evolution already exist in the human gene pool.


There are two ways we want to eliminate these defective genes. One is to optimize them by mutating the genes of our offspring. Another way is through more and more advanced gene technology. In the future, human beings may use gene editing technology to continuously optimize human genes, so that all kinds of defective genes can be removed from our gene pool. At that time, human beings will become more advanced life.

At present, the global population has reached 7.8 billion, which is still growing rapidly. It is estimated that by 2100, the world population will reach 11 billion. Scientists believe that the earth’s capacity for population is about 10 billion. If it exceeds this number, the earth’s ecology will face great pressure. Overpopulation is also a major human survival crisis.

To get rid of the survival crisis caused by overpopulation, the only way is to realize space colonization. Only when we become an interstellar civilization can we colonize more living planets in the universe. It is only 80 years from 2100 to now that we can solve the various crises brought about by the growing population. If after 80 years, human beings have not been able to migrate to other planets, then we will face a major crisis caused by overpopulation.

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