If the end of the world comes, how many people, at least, will be needed to continue the human race?

You might not imagine that it doesn't take very, very many people to continue the human race as you might think.

There are so many end-of-the-world scenarios in movies and TV shows, and the environment of the earth is deteriorating in real life, so we can't help but worry. Whether it is a biological crisis or a super earthquake, or climate deterioration, humans always have the instinct to survive and the desire to continue the race. So, if the end of the world does happen, how many people do we need, at least, to be able to continue the human race?

A recent study shows that although it seems that today's society is diverse and complex, with all three religions and all kinds of people. But if it does come to a critical situation, it may not take that many people.

Cameron Smith, an adjunct assistant professor in the Department of Anthropology at Portland State University in Oregon, recently conducted a study that concluded that even if only a few hundred humans were left, our race might still be strong enough to persist for several hundred years. It seems that the human race is more alive than we thought.

Of course, it depends on what the factors leading to the end of the world are in the first place. Because such a factor may not be a quick fix, there may also be many long effects. Take nuclear war, for example, even if the world's nuclear bombs have exploded, but the residual nuclear radiation will continue to cause lasting damage to humans for quite some time. Or perhaps the earthquakes and explosions brought on by an asteroid impact on Earth would also raise dust that would block out sunlight and cause temperatures to drop and plants to die ......

To simplify this study, Smith made the assumption that the side effects of these disasters would be ignored for the time being, or the assumption was how many people would be left to continue the human race after all the side effects were over. It turns out that this number is indeed too small compared to the current total population of 7.8 billion, but much depends on how the survivors survive.

He believes that staying in the big cities is not the best choice for these survivors and that the cities that seem to be bustling and bustling today are rather more vulnerable at the end of the world. The city is very dependent on the supply of electricity to run, and on that day, the power plant will not be able to run. Moreover, the city relies on outside transportation for food and will be out of food by then.

In contrast, returning to the village seems to be a better choice. He remembered the early Neolithic period, that is, about 12,000 years ago. Humans at that time all survived in small primitive villages with populations ranging from a few hundred to a thousand people, and they were able to live well and eventually carried on, developing into the huge race we have today.

In this case, there is a very noteworthy problem, and that is inbreeding.

Everyone should have heard about the dangers of inbreeding, which can lead to the combination of many unfavorable recessive genes that can lead to deformities and even death in newborns. The most famous case of inbreeding in the world is the Habsburg dynasty of Spain. This dynasty maintained the practice of marrying within the family for a long time and eventually died in 1700 due to extinction. Many of the monarchs before that were plagued and harmed by genetic diseases.

Smith speculated that even in the early Neolithic period, those ancient villages may have married each other, thus avoiding the troubles associated with consanguineous marriage. For people living at the end of the world, this is one of the problems that the total population is too small to have to face.

This is also an important factor affecting the number of people needed to continue the human race. Maybe a few fewer people can survive, but then the harm of inbreeding will not be avoided. If the size of the population is large enough, the health of newborns can also be effectively protected. That's why he claimed that several hundred people would be needed to continue the human race for hundreds of years.

However, Frédéric Marin, an astrophysicist at the University of Strasbourg in France, pointed out in a 2018 study that there is another way for humans to survive, and that is to take refuge on a spaceship on other planets. He believes that if the end of the world does play out, then survivors could make their escape to Proxima b with the technology available to humans.

Proxima b is also known as the three-body planet described by Liu Cixin in "Three Bodies" and was discovered only after the publication of this novel. It is an Earth-like planet, and the surface temperature is still promisingly habitable. It is also the closest exoplanet to us and is one of the most suitable objects for human refuge.

According to Marin's proposal, the survivors could then travel to the three-body planet in a state-of-the-art spacecraft. Moreover, a minimum of 98 people on board this spacecraft would be enough to last for a voyage of up to 6,300 years, allowing descendants to reach Proxima b by passing it down from generation to generation. Of course, these 98 people would not be chosen completely at random, but rather 49 unrelated male and female pairs, thus avoiding consanguineous marriages.

This is just the minimum number, and the more the merrier if possible, of course. In February of this year, Marin published a paper saying that it would be better if the initial number could reach 500, to ensure the diversity of genetic material.

Smith, after reading Marin's paper, elaborated on the same view. He made an analogy that it is like having a plane that is going to New York, then this crew can't fill the airliner with the fuel that happens to arrive in New York. The spare fuel can also prevent accidents in case of weather changes and other conditions. So even though 98 or a few hundred people would be able to continue the human race, if the end of the world does occur, more survivors would be better.

But you may also have noticed: it is also apparently impossible with current human technology to take 98 or even more people into space at the same time, as Marin says, and to travel to Proxima b in 6300 years. And studies now also point out that the environment on Proxima b may be quite harsh and unsuitable for human survival. All said and done, this plan does not look very feasible at the moment.

That's why Seth Baum, co-founder and executive director of the Global Catastrophic Risk Institute, points out that it's much more reliable to have some extra shelter on Earth than to voyage to another planet. We need to choose an isolated environment, such as an isolated island, to get away from possible disasters, which is the last place of refuge for human beings.

He also believes that we could establish specialized catastrophic shelters, like a doomsday seed bank near the Arctic Circle, as the last retreat for humanity. After all, just keeping seeds may not be enough, and more resources are needed to facilitate the last humans.

When all is said and done, it's really about how to avoid the end of the world. These means of preserving to the last, no matter how effective, we hope they don't have the chance to be used. The best outcome would be to keep the Earth's environment going.