The minimum number for our species to survive is very small, compared to about 7.8 billion people living on Earth today.
Nuclear war, the attack of a giant asteroid… it is not difficult to imagine a scenario in which human life on Earth could suddenly end. But assuming there are some survivors, how many will it take to keep our species going?
The short answer is that it depends on many factors. Different disasters will create different apocalyptic conditions for surviving human populations to endure. For example, a nuclear war could trigger a nuclear winter, exposing survivors to freezing summer temperatures and global famine, not to mention exposure to with radiation. However, putting some of these conditions aside and focusing on population size, the minimum number for our species to survive is very small compared to the approximately 7.8 billion people living on Earth. Earth today.
Research on this issue was conducted by Cameron Smith, assistant professor in the Department of Anthropology at Portland State University in Oregon, USA.
He found the answer through the study of the first human civilizations and the colonization of space over time, thereby providing an insight into the hope of mankind’s survival. after the apocalypse. In Smith’s view, the big cities would be most vulnerable if global civilization collapsed, since that’s where most of the food is imported and is heavily reliant on electricity. As a result, surviving populations will likely scatter out of cities in search of resources.
During the early Neolithic period (which started when the last ice age ended, about 12,000 years ago) when humans started farming, there were many small villages around the world with populations ranging from hundreds to about 1,000 individuals.
“Those are fairly independent populations, but I suspect they also have livestock links and marriage connections to other villages. And in an apocalyptic scenario, I imagine the same thing would happen. “, Smith shared.
And a population of just a few hundred survivors is enough to sustain a livestock system. But inbreeding or crossbreeding between closely related individuals is a major challenge faced by small populations.
The consequences of inbreeding can be demonstrated by the fall of the Habsburg dynasty, which ruled Spain during the 16th and 17th centuries. This dynasty regularly maintained inbreeding until 1700. , when the bloodline ended with King Charles II suffering from infertility and facial disfigurement.
A similar scenario could play out with a dwindling human population with limited breeding options after the apocalypse, unless they have enough genetic diversity to avoid close associations. There should be a sufficient number of individuals of the opposite sex of reproductive age, known as the effective population size, for successful mating to take place.
“Humans have the ability to prepare populations to survive the apocalypse if they perceive it to be coming,” said Seth Baum, co-founder and chief executive officer of the Global Disaster Risk Institute, a private organization. nonpartisan consultation, recognizing the risk of global catastrophe.
He advocates that averting potential disasters, for example in the case of nuclear war, means ensuring good relations between countries with nuclear weapons. However, Baum’s research also includes the prospect of building shelters to protect people in the event of a global disaster.
“If a disaster was imminent, we would want some kind of protection like this, so that at least part of the population could continue, and human civilization could continue,” Baum said.
According to Baum, a key element in any form of refuge is the ability to insulate a group from whatever it is doing. For example, certain island nations, such as New Zealand and Australia, have effectively turned themselves into large-scale shelters during the COVID-19 pandemic.
One more step, Baum says, is to have a disaster shelter somewhere on Earth. He compared this hypothetical refuge to the global seed vault, located in Svalbard, Norway, which keeps backup copies of the world’s seeds safe inside a mountain.
“And then, more ambitiously than that, would be to have something for the case that humans are no longer on this planet,” Baum said.
And in another hypothetical situation, when humans were trying to escape to another celestial body or planet to avoid the apocalypse, what would be the minimum number of people needed to survive in space?
According to a 2018 study published in the Journal of the British Interplanetary Society, led by Frédéric Marin, an astrophysicist at the University of Strasbourg in France who studies cosmic anthropology. This number is not large.
Specifically, a starting crew of just 98 people would be enough for a 6,300-year journey (traveling in a hypothetical spacecraft at the speed of current technology) to Proxima Centauri b, a planet. Earth-like habitable planet, orbiting Proxima Centauri, the closest star to the sun.
And the Proxima Centauri b crew will include not a random sample of 98 people, but 49 unrelated crossbreeding pairs, ready to pass on their genes. Populations will only be genetically diverse and healthy over time under certain conditions. So, the crossbreeding of the crew will have to be monitored and limited.
Also, if conditions are better, a starting group larger than 500 people may be a safer choice, as they will be more likely to keep their genetic diversity with more crossbreeding pairs. , according to a follow-up study by Marin and colleagues.
However, Smith’s view recommends against using absolute minimums in spatial endeavors.
“The analogy is like you get on a plane and they take you to New York. You wouldn’t want the pilot to have just enough precision fuel to get to the runway in New York. Always have a reserve in case of disaster.” , he said.