Humanity’s last near-extinction shows how it might survive the next one

By Robert A. Vella

About 75,000 years ago, a supervolcano erupted at what is now Lake Toba on the Indonesian island of Sumatra.  This was a catastrophic explosion so massive that it plunged the world into a prolonged period of darkness that quickly killed-off much of the Earth’s photosynthetic plant life and lowered global temperatures for hundreds of years.  As their food sources disappeared, the decline of many animal species soon followed.  The effects are similar to what has been predicted for a nuclear war, commonly known as a “nuclear winter.”

At that time, Homo sapiens were primitive hunter-gatherers in the midst of migrations out of Africa.  DNA evidence indicates that our species nearly went extinct after the eruption.  A “genetic bottleneck” occurred which may have reduced the human population to as few as 2,000 individuals.  But, we managed to survive;  and, that remnant population was sufficient to restart our evolution.

Now, humanity appears to be facing another extinction threat within this century which author Elizabeth Kolbert detailed as the sixth mass extinction event in Earth’s history.  From:  Reducing the Risk of Human Extinction

In their catalogs of extinction risks, Britain’s Astronomer Royal, Sir Martin Rees (2003), gives humanity 50-50 odds on surviving the 21st century; philosopher Nick Bostrom argues that it would be “misguided” to assume that the probability of extinction is less than 25%; and philosopher John Leslie (1996) assigns a 30% probability to extinction during the next five centuries. The “Stern Review” for the U.K. Treasury (2006) assumes that the probability of human extinction during the next century is 10%.

So, if this threat is realized, how many of us would need to survive to continue our species?  From:  Catastrophe, Social Collapse, and Human Extinction

It seems that groups of about seventy people colonized both Polynesia and the New World (Murray-McIntosh, Scrimshaw, Hatfield, & Penny, 1998; Hey, 2005). So let us assume, as a reference point for analysis, that the survival of humanity requires that one hundred humans remain, relatively close to one another, after a disruption and its resulting social collapse. With a healthy enough environment, one hundred connected humans might successfully adopt a hunter-gatherer lifestyle. If they were in close enough contact, and had enough resources to help them through a transition period, they might maintain a sufficiently diverse gene pool, and slowly increase their capabilities until they could support farming.

This analysis focuses entirely upon organic human survival on Earth’s surface.  While it is at least possible that isolated enclaves could support small tribes of hunter-gatherers, there is no certainty that would happen.  The unknown variable at this point is how catastrophic will climate change become.  In the event that wiped-out the dinosaurs 66 million years ago, about 75% of all species went extinct including all four-limbed vertebrates (i.e. tetrapods) over 55 lbs. except for a very few number of species (e.g. crocodiles, sea turtles).  In the event known as the Great Dying around 252 million years ago, 96% of all marine species disappeared and the only known mass extinction of insects occurred.  Therefore, the possibility of organic human survival is conditional upon the severity of climate change impacts as well as upon the exact nature of those impacts.

However, what did not happen during the Toba supereruption 75,000 years ago which would undoubtedly happen in the 21st century is artificial human survival underground and in remote sanctuaries.  During the Cold War, the U.S. government and other governments around the world began building underground shelters to protect some public officials and private citizens in case of nuclear war.  One such secret installation which was later exposed is the Greenbrier Resort in West Virginia.  It is reasonable to assume that this government-sponsored underground survival strategy has continued and has likely escalated as the existential dangers posed by climate change have become clearer.  Additionally, it is widely known now that very rich people around the world have been making sophisticated doomsday preparations such as purchasing land in remote areas and taking other extreme measures to ensure their personal survival.  Depending on the circumstances, some of their efforts might be successful.

In conclusion, despite the great uncertainty for the century ahead, some humans will probably survive the currently developing extinction event at least for a while.  For them, the inevitable question might become whether or not survival under those conditions was a good idea.