Just the two of us: The last couple on earth in a post-apocalyptic world. Will they be able to revive all of humanity?

Many people think that a single pair of a new Adam and Eve won’t be able to resume life on earth, and make several assumptions about this. Let’s look at the most significant of them.

Fatal mutation

It is believed that after several generations, inbreeding, the crossing of closely related forms within the same population of organisms, will lead to the occurrence of some kind of fatal mutation and will kill all future offspring.

In the first generation (the first two people), even a serious and fatal mutation such as cystic fibrosis will be passed on to 50% of the offspring, and those who have it will still have a good chance of surviving to adulthood (and being able to reproduce). A much more serious risk in this case would be the death of the mother during childbirth.

Genetic diversity

Two random people will not have enough genetic diversity between them. This will lead to the problem of genetic variation. The truth is that some degree of inbreeding is relatively common and rarely very harmful. Assortative mating (or homogamy) means that we seek out partners who are genetically similar to us. Although the two would likely experience inbreeding depression as time went on, that was something that many isolated villagers faced, and they were not doomed to extinction.

Even if this led to a decrease in the chances of survival, this would not mean that any generation would become the limit of survival. Humans will lose a huge amount of genetic diversity, but it will gradually improve over time as a result of random mutations that will help weed out harmful genes through natural selection.

Absence of realization

Endangered humans will respond in the same way as other endangered mammals. Endangered animals don’t realize they are endangered, so using them as case studies is not a good comparison. It is clear that animals will not change their behavior to compensate for their endangered status. People who have realized the fact that they are the last ones left will be quite intelligent and will reproduce as much and as often as possible.

In our theoretical world of the best possible circumstances, a particularly dangerous pandemic occurs on Earth, wiping out every person on the planet.

Two astronauts (a man and a woman) return to Earth after several months in space and discover that there are no people left on Earth.

Luckily for them, they can collect canned goods from all over the world and live in any house they like. Thanks to the availability of libraries with books, they can independently master the basics of medical care and agriculture, and ultimately become self-sufficient people.

In addition, human-specific viruses cannot exist for long without their host (about two days to a week), most threats of viral diseases will be eliminated.

These two people will realize that they need to continue the human race and they decide to have as many children as possible to maintain the diversity they both offer. They had nine children before becoming infertile. Early generations face many challenges, including relatively high early mortality rates, but are able to thrive despite setbacks due to their adaptive intelligence. Tens of thousands of years pass, but over time the gene pool diversifies and people spread out, populating new cities, eventually migrating to other continents.

As long as the apocalypse does not shake the foundations of modern civilization, humanity can recover surprisingly quickly. At the turn of the 20th century, the North American Hutterite society – highly inbred, by the way – achieved its highest level of population growth ever, doubling every 17 years. And if every woman gave birth to eight children, we would reach a population of seven billion and the modern overpopulation crisis in just 556 years.

So the answer is yes – there are many stories of incredible journeys from the end of the world and it is possible that two people could survive and repopulate the Earth.