Human Extinction: The Uncertainty of Our Fate

By –Mahboob Ali Khan,MHA,CPHQ

Extinction marks the evolutionary death of a species. Observing the fates of many species ancient and recent, it appears to be Nature’s mechanism of periodically clearing out the outdated to make room for the fit. But is extinction necessarily inevitable for every species? More specifically, are humans destined to meet an unavoidable end?  Extinction, Then and Now

Perhaps the most studied extinction — in textbooks, grade-school computer games, and movies alike — has been the extinction of the dinosaurs, one among many constituting the Cretaceous-Tertiary mass extinction around 65.5 million years ago. Theorized to have been the result of a 20-kilometer-wide meteorite’s impact at the Yucatan peninsula, it sits among the five major mass extinctions that have occurred in the Earth’s 4.6 billion-year history: the Ordovician-Silurian extinction , the late-Devonian extinction , the Permian-Triassic extinction, the end-Triassic extinction, and the Cretaceous-Tertiary extinction .All five mass extinctions of the past have been attributed to major geographic and climatic changes on Earth — significant fluctuations in sea levels, erupting volcanoes, extra-terrestrial impact — and are believed to have forced the extinction of up to 95 percent of all species at a time. Not all extinction, however, is so spectacularly concentrated. As shown in fossil records and on present-day Earth, extinction is historically an ever-present phenomenon, although extinction rates fluctuate over time.

A microbiologist examines reconstructed 1918 Pandemic Influenza Virus. The epidemic killed up to 50 million people worldwide.

If this is true, could humans be the dinosaurs of this next mass extinction, and if so, what would be the final nail in our coffin? A small sample of Dartmouth students was asked these questions .The following is a compilation of their general responses, followed by some analysis.RIP Homo sapiens

A pandemic will kill off all humans.In the past, humans have indeed fallen victim to viruses. Perhaps the best-known case was the bubonic plague that killed up to one third of the European population in the mid-14th century While vaccines have been developed for the plague and some other infectious diseases, new viral strains are constantly emerging — a process that maintains the possibility of a pandemic-facilitated human extinction.Some surveyed students mentioned AIDS as a potential pandemic-causing virus.  It is true that scientists have been unable thus far to find a sustainable cure for AIDS, mainly due to HIV’s rapid and constant evolution. Specifically, two factors account for the virus’s abnormally high mutation rate: 1. HIV’s use of reverse transcriptase, which does not have a proof-reading mechanism, and 2. the lack of an error-correction mechanism in HIV DNA polymerase.. Luckily, though, there

are certain characteristics of HIV that make it a poor candidate for a large-scale global infection: HIV can lie dormant in the human body for years without manifesting itself, and AIDS itself does not kill directly, but rather through the weakening of the immune system. However, for more easily transmitted viruses such as influenza, the evolution of new strains could prove far more consequential. The simultaneous occurrence of antigenic drift (point mutations that lead to new strains) and antigenic shift (the inter-species transfer of disease) in the influenza virus could produce a new version of influenza for which scientists may not immediately find a cure. Since influenza can spread quickly, this lag time could potentially lead to a “global influenza pandemic,” according to the Centers for Disease Control and Prevention . The most recent scare of this variety came in 1918 when bird flu managed to kill over 50 million people around the world in what is sometimes referred to as the Spanish flu pandemic. Perhaps even more frightening is the fact that only 25 mutations were required to convert the original viral strain — which could only infect birds — into a human-viable strain .

Another superior species will evolve and usurp man’s place on earth.While it has never been formally proven, many hold the anthro-centric belief that Homo sapiens are superior to other earthly life forms. Those who believe this often cite man’s complex cognitive ability as the selective bias that differentiates humans from other organisms . Though this may be true to a certain degree, it has been proven that animals such as monkeys have some of the same psychological biases as humans, such as loss-aversion and anchoring bias . Perhaps more convincing for the case of human domination is the argument that humans are ‘superior’ for their ability to “change the environment” to a greater degree than any other species . That is, we as humans have exceeded other living organisms in using natural resources and adapting the environment to our needs. At least on Earth, there does not appear to be a major threat to humans’ superiority in this sense. However, the idea behind panspermia may deem a super-human threat possible. Panspermia is the theory that the beginnings of life originated elsewhere in the universe and were brought to our planet by some extraterrestrial means (i.e. a

meteorite) . This theory has been largely disregarded for two primary reasons: 1. Miller’s experiment that supported abiogenesis (the formation of amino acids from inorganic matter present on early Earth) and 2. the general lack of proof of an extraterrestrial vehicle . However, should panspermia be true, it is possible that an extraterrestrial rock could introduce a new life form to Earth that could take over humans’ role on Earth.

The population will grow until all natural resources are expended.This topic is a hotly debated one, particularly in light of related arguments for population control. Those who predict a shortage of natural resources believe in the limited carrying capacity of our planet. For instance, with renewable freshwater, Joel Cohen estimates that the Earth may only be able to support 5.3 to 8.2 billion people, assuming a low estimate for the amount of freshwater available and a high estimate for the amount of water necessary to human sustenance . Considering that the world population is already 6.7 billion, a growing world population could be a problem, and as of 2008, the human population has indeed been growing at a rate of 1.188 percent . Moreover, over the last fifteen years, the amount of energy consumed has grown at a slightly higher rate than has the amount of energy produced .On the other hand, though the world population is growing, this growth rate has steadily decreased over the last forty years. In fact, some countries such as Japan and Germany currently have declining population numbers . Moreover, some like economist Julian Simon even argue that a higher population will give rise to greater innovation, allowing the world’s population to discover technologies that will help us circumvent the Earth’s natural limitations .Man will destroy himself.Another possibility is the death of mankind at the hands of its own weapons. One threat lies in the use of weapons of mass destruction, internationally referred to as CBRN (Chemical, Biological, Radiological, and Nuclear) warfare. Chemical warfare revolves around the use of toxic, non-living agents (mustard, cyanides), while biological warfare involves the use of living organisms and/or toxins that they produce (anthrax, botulinum toxin) (20). Though both could potentially bring

about human extinction, radiological and nuclear warfare have been referred to most often when considering a potential “Doomsday Machine/Device.”Two prominent candidates for the Doomsday Machine have emerged over the last 60 years. First was the “dead hand,” a rumored underground Soviet monitoring system whose central computer Perimetr would have facilitated the automated detonation of an extensive nuclear weapons network, had the Soviet Union come under attack during the Cold War . Though constructed in the 1970s, dead hand is still armed and operational, according to a 2007 article in the New York Times, and has been declared a possible Doomsday Machine . 

The other contender is the theoretical cobalt bomb. Essentially, the cobalt bomb is an atomic bomb covered in cobalt-59. When bombarded with neutrons, the outer shell of cobalt-59 is converted into the highly radioactive isotope cobalt-60. Cobalt-60, as opposed to other radioactive isotopes, has a relatively long half-life of 5.3 years that would cause the deleterious effects of a cobalt bomb’s radiation to be both long-lasting and global if properly dispersed – a surefire recipe for global extinction. Thus, while the subject of a man-made human apocalypse seems like the stuff of science fiction, it may not be so farfetched. However, for obvious reasons, it is also fair to say that these potential planet-enders have yet to be successfully tested or implemented. 

References1. M. Boulter, Extinction (Columbia University Press, New York 2002).

2. L. Siegel, The Five Worst Extinctions in Earth’s History (2000). Available at

http://www.space.com/scienceastronomy/planetearth/extinction_sidebar_000907.html (5 March

2009).

3. N. Campbell et al., Biology: Concepts & Connections, Sixth Edition (Pearson Eduction, Inc.,

California 2009).