Human extinction

Human extinction is the end of the human species. Various scenarios have been discussed in science, popular culture and religion (see End time). The scope of this article is existential risks. Humans are very widespread on the Earth, and live in communities that (while interconnected) are capable of some level of basic survival in isolation. Therefore, pandemics and deliberate killing aside, to achieve human extinction the entire planet would have to be rendered uninhabitable by humans, with no opportunity provided or possibility for humans to establish a foothold beyond Earth. This would typically be during a mass extinction event, a precedent of which exists in the Permian–Triassic extinction event among other examples.

In the near future, anthropogenic extinction scenarios exist: global nuclear annihilation, dysgenics, overpopulation,^[1] biological warfare or an accidental pandemic, ecological collapse, and global warming; in addition, emerging technologies could bring about new extinction scenarios, such as advanced artificial intelligence or self-replicating nanobots. Natural scenarios, such as meteor impact and large-scale volcanism, may be of less concern than anthropogenic scenarios: while naturally-caused extinction scenarios have occurred multiple times in the geologic past, the probability of recurrence within the human timescale of the near future is negligibly small. As technology develops, there is a theoretical possibility that humans may be deliberately destroyed by the actions of a nation state, corporation or individual. There is also a theoretical possibility that technological advancement may resolve or prevent potential extinction scenarios. The emergence of a pandemic of such virulence and infectiousness that very few humans survive the disease is a credible scenario. While not necessarily a human extinction event, this may leave only very small, very scattered human populations that would then evolve in isolation. It is important to differentiate between human extinction and the extinction of all life on Earth. Of possible extinction events, only a pandemic is selective enough to eliminate humanity while leaving the rest of complex life on earth relatively unscathed.

Possible scenarios

Severe forms of known or recorded disasters

• Nuclear or biological warfare; for example, a future arms race results in much larger arsenals than those seen during the Cold War.^[2] See World War III.
• Pandemic^[2] involving one or more viruses, prions, or antibiotic-resistant bacteria. Past examples include the Spanish flu outbreak in 1918 and the various European viruses that decimated indigenous American populations. A deadly human-only pandemic would be self-limiting as it reduces the density of its target population, but a pathogen with a wide host range in multiple species could reach even isolated humans by using insects or other animals as "carriers".^[3]
• Geological and Cosmological disasters

U.S. officials assess that an engineered pathogen capable of "wiping out all of humanity" if left unchecked is technically feasible and that the technical obstacles are "trivial". However, they are confident that in practice, countries would be able to "recognize and intervene effectively" to halt the spread of such a microbe and prevent human extinction.^[4]

Habitat threats

• The presence of 16 multiplicative self-reinforcing positive feedback loops in climate change, and the finding that we are close to the inner limit of the "Circumstellar habitable zone^[5]", looking at the deep past, correlating CO2 levels with temperature and sea level rise, has been used as evidence of near-term human extinction. There is a 40-year lag in the consequences of emissions and temperature rise. We are locked into consequences with 0.8 degrees C, with current temperature increase resulting from 40 years ago. In the last 29 years, we have seen a greater increase in CO2 emissions than in the last 100 years.
• In around 1 billion years from now, the Sun's brightness will increase as a result of a shortage of hydrogen and the heating of its outer layers will cause the Earth's oceans to evaporate, leaving only minor forms of life.^[6] However, well before this, the level of carbon dioxide in the atmosphere will be too low to support plant life, destroying the foundation of the food chains.^[7] See Future of the Earth.
• About 7–8 billion years from now, after the Sun has become a red giant, the Earth will probably be engulfed by an expanding Sun and destroyed.^[8][9]

Population decline

• Preference for fewer children; if historical developed world demographics are extrapolated they suggest extinction before 3000 CE. (John A. Leslie estimates that if the reproduction rate drops to the German level the extinction date will be 2400.) However, evolutionary biology suggests the demographic transition may reverse itself; conflicting evidence suggests birth rates may be rising in the 21st century in the developed world.^[10] Whereas the work of Hans Rosling, a Swedish medical doctor, academic, statistician and public speaker predicts Global populations peaking at less than 12 billion.^[11]

Scientific accidents

• The creators of the first "superintelligent" entity could make a mistake and inadvertently give it goals that lead it to immediately "annihilate" the human race.^[2][12]
• In his book Our Final Hour, Sir Martin Rees claims that without the appropriate regulation, scientific advancement increases the risk of human extinction as a result of the effects or use of new technology. Some examples are provided below.
  • Uncontrolled nanotechnology (grey goo) incidents resulting in the destruction of the Earth's ecosystem (ecophagy).
  • Creation of a "micro black hole" on Earth during the course of a scientific experiment, or other foreseeable scientific accidents in high-energy physics research, such as vacuum phase transition or strangelet incidents. There were worries concerning the Large Hadron Collider at CERN as it is feared that collision of protons at a speed near the speed of light will result in the creation of a black hole, but it has been pointed out that much more energetic collisions take place currently in Earth's atmosphere.

Near-Earth object

Near-Earth objects (NEOs), serve as an absolute threat to the survival of living species, and that even small-scale events caused by one can result in a substantial amount of local and regional damages.^[13] Because there are very few extraterrestrial impacts ever recorded in Earth’s history, there are no casualties in recorded history due to such impacts. However, a single, extraterrestrial event^[14] can lead to the accumulation of more deaths and destruction than any man-made war or epidemic could ever produce. One mitigation technique includes the Kinetic impactor. Such a device is established on a momentum transfer, all caused by a durable spacecraft that is practically designed and sent out to crash onto the asteroid at high velocity (10 km/s), hoping that it will marginally change its orbit. During this process, what must be noted and paid attention to is that a second observer spacecraft is also present and vital in precisely calculating the resulting change in the asteroid’s orbit. In supplement to the Kinetic impactor, a second safety mechanism is commonly referred to as the Nuclear Blast Deflection technique. Hypothetically speaking, if one were to utilize a particular thermonuclear warhead for a nuclear detonation, NEOs of about 150–200 meters in diameter could be deflected by about 10 cm/s. In addition to the Kinetic impactor and Nuclear Blast Deflection techniques, a third possibility is famously regarded as the "gravity tractor." A gravity tractor is a man-made device placed in the vicinity of the NEO and seeks to alter the projected trajectory of the object.^[15]

Scenarios of extraterrestrial origin

• Major impact events.
• Gamma-ray burst in our part of the Milky Way. (Bursts observable in other galaxies are calculated to act as a "sterilizer", and have been used by some astronomers to explain the Fermi paradox.) The lack of fossil record interruptions, and relative distance of the nearest Hypernova candidate make this a long term (rather than imminent) threat.
  • Wolf-Rayet star WR 104, which is 8000 light years from the Sun, may produce a gamma ray burst aimed at the Sun when it goes supernova.^[16][17]
• Invasion by militarily superior extraterrestrials (see alien invasion) — often considered to be a scenario purely from the realms of science fiction, professional SETI researchers have given serious consideration to this possibility, but conclude that it is unlikely.

Other

• Modification of humans into a new species
  • Technological transition into a posthuman life-form or existence.
    • Commentators such as Kevin Warwick point to the possibility of humans evolving by linking with technology;^[18] while others have argued that humanity will inevitably experience a technological singularity, and furthermore that this outcome is desirable (see singularitarianism).
  • Biological evolution of humanity into another hominid species. Humans will continue to evolve via traditional natural selection over a period of millions of years, and Homo sapiens may gradually transition into one or more new species.

Perception of human extinction risk

It is possible to do something about dietary or motor-vehicle health threats. It is much harder to know how existential threats should be minimized.

Some Behavioural finance scholars claim that recent evidence is given undue significance in risk analysis. Roughly speaking, "100 year storms" tend to occur every twenty years in the stock market as traders become convinced that the current good times will last forever. Doomsayers who hypothesize rare crisis-scenarios are dismissed even when they have statistical evidence behind them. An extreme form of this bias can diminish the subjective probability of the unprecedented.

In 2010 Australian virologist Frank Fenner, notable for having a major role in the eradication of smallpox, predicted that the human race would be extinct in about a century.^[19]

Observations about human extinction

David M. Raup and Jack Sepkoski claim there is a mysterious twenty-six-million-year periodicity in elevated extinction rates.^[20]

Milankovitch cycles are under the category of periodicity. These cycles describe the way that the earth moves and how the climatic changes vary depending on where the earth is in space. The orbital shape of the earth causes changes every 100 thousand years. The axial tilt of the earth "wobbles" and alters the climate every 41 thousand years. The axial precession is the process in which the climate will change in terms of how the earth rotates about its own axis. Raup did find that every 26 million years, there will be a mass extinction. Roland Jansson and Mats Dynesius in their article The Fate of Clades in a World of Recurrent Climatic Change: Milankovitch Oscillations and Evolution,^[21] discuss how these cycles will cause orbitally forced range dynamics (ORD) in which the climate changes induced by the Milankovitch cycles cause changes in the geographic distribution of clades. Clades are a group of organisms that are theorized to have to have evolved from a common ancestor.

Milankovitch cycles, or more commonly known as Quaternary Climatic Oscillations as described by Barker, P. A., et al. in Quaternary Climatic Instability in South-East Australia from a Multi-Proxy Speleothem Record,^[22] effect the climate in various ways in either extreme cold or extreme heat.

Jared Diamond's The Third Chimpanzee estimates that 64% of hunter-gather societies engage in warfare every two years. The combination of inventiveness and the history of violence in humans has been cited as evidence against its long term survival.

Carl Sagan wrote:

If we are required to calibrate extinction in numerical terms, I would be sure to include the number of people in future generations who would not be born.... (By one calculation), the stakes are one million times greater for extinction than for the more modest nuclear wars that kill "only" hundreds of millions of people. There are many other possible measures of the potential loss—including culture and science, the evolutionary history of the planet, and the significance of the lives of all of our ancestors who contributed to the future of their descendants. Extinction is the undoing of the human enterprise.^[23]

Omnicide

Omnicide is human extinction as a result of human action. Most commonly it refers to extinction through nuclear warfare or biological warfare,^[24][25][26] but it can also apply to extinction through means such as global anthropogenic ecological catastrophe,.^[27]

Omnicide can be considered a subcategory of genocide.^[28] Using the concept in this way, one can argue, for example, that:

Proposed solutions

Scientists such as Stephen Hawking have proposed that an initiative to colonize other planets within the solar system could improve the chance of human survival.

See also

• Global catastrophic risks
• Ecocide
• Extinction event
• Mutual assured destruction
• Space and survival
• Doomsday argument
• Toba catastrophe theory
• Voluntary Human Extinction Movement

Notes

References

Further reading

• Leslie, John. (1996). The End of the World: The Science and Ethics of Human Extinction. Routledge. ISBN 0-415-18447-9
• Rees, Martin. (2003). Our Final Hour: A Scientist's Warning: How terror, error, and environmental disaster threaten humankind's future in the century--on Earth and beyond. Basic Books. ISBN 0-46506862-6.
• Michael Moyer (September 2010). "Eternal Fascinations with the End: Why We're Suckers for Stories of Our Own Demise: Our pattern-seeking brains and desire to be special help explain our fears of the apocalypse". Scientific American. 

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