The Feasibility of Repopulating Humanity with a Small Population

Could a small group, consisting of one man and seven women, repopulate humanity in the event of an extinction event? This article explores the feasibility of such an endeavor, examining the genetic and health risks associated with inbreeding and the historical context of population bottlenecks.

Introduction

The concept of repopulating a completely devastated Earth with a small group of individuals is intriguing but fraught with challenges. One common argument is that with just a few hundred people, the genetic pool would be sufficiently diverse to avoid serious genetic problems. However, the situation becomes much more complex with only eight individuals, especially when discussing inbreeding.

The Role of Inbreeding

Inbreeding among a small group, such as one man and seven women, would inevitably lead to genetic problems. When two half-siblings or more have children together, the risk of inheriting harmful recessive traits increases significantly. This is because these traits are more likely to manifest when the same gene appears in both parents, passed on from the common ancestor.

The inbreeding coefficient, which measures the probability that two alleles in an individual are identical by descent, increases exponentially with each generation. In a small group, the inbreeding coefficient can quickly reach very high levels, leading to a drastically decreased genetic diversity. This reduces the population's ability to adapt to new environments and increases susceptibility to diseases.

Risk and Health Implications

Studies on inbreeding have shown that offspring resulting from close inbreeding are more likely to suffer from genetic disorders, birth defects, and mental health issues. The cumulative effect of a few generations of inbreeding can lead to a population of individuals who are physically and mentally weaker, with a higher risk of genetic abnormalities.

A notable example of this is the Neanderthals, who may have become extinct due to genetic incompatibilities and a weakened immune system resulting from inbreeding. By the time these genetic issues became overt, it might have been too late to reverse the situation.

Minimum Population for Genetic Safety

Such risks highlight the need for a minimum population size to ensure genetic safety. Population genetics studies have suggested that a minimum of approximately 1000 to 2000 individuals would be required to avoid severe genetic problems. This is based on the concept of the effective population size, which measures the size of a population acting as a gene pool.

One study, conducted in Italy, set the minimum for safe repopulation or colonization at around 110 individuals, with a recommendation of 10 men and 100 women. This recommendation includes genetic pre-screening and a tightly controlled "breeding plan" for several generations to ensure the genetic health of the population. Such screening would involve identifying and eliminating harmful recessive traits, ensuring a diverse and healthy genetic pool.

Conclusion

In conclusion, while it is possible for a small group of individuals, such as one man and seven women, to repopulate the Earth, it would be highly risky and likely to result in serious genetic and health issues. Historical examples and genetic studies suggest that a much larger, genetically diverse population is necessary to ensure the long-term survival and health of humanity. If such a small group were to attempt repopulation, it would be crucial to have access to genetic screening, a breeding plan, and extensive resources to mitigate the risks of inbreeding.