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 which (whilst interconnected) are capable of some kind of basic survival in isolation. Therefore, pandemics and deliberate killing aside, to achieve human extinction, the entire planet would have to be rendered uninhabitable, with no opportunity provided or possible 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, total global war, overpopulation or global accidental pandemic; besides natural ones: Meteor impact and large scale volcanism; and anthropogenic-natural hybrid events like global warming and catastrophic climate change. Naturally caused extinction scenarios have occurred multiple times in the geologic past although the probability of reoccurrence within the human timescale of the near future is infinitesimally 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 in a form of global suicide attack. 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.
1 Possible scenarios
1.1 Severe forms of known or recorded disasters,
1.2 Long-term habitat threats,
1.3 Population decline,
1.4 Scientific accidents,
1.5 Scenarios of extraterrestrial origin,
2 Perception of human extinction risk,
3 Observations about human extinction
3.1 Quantifying the Impact,
4 In popular culture,
5 See also,
8 Further reading,
See also: Risks to civilization, humans and planet Earth
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. See World War III.,
Pandemic involving one or more viruses, prions, or antibiotic-resistant bacteria. Past examples include the Spanish flu outbreak in 1918 and the various European viruses which decimated indigenous American populations. A deadly human-only pandemic would be self-limiting as it reduced 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".,
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.
Long-term habitat threats:
In about 1 billion years from now, the Earth's oceans will disappear, due to the Sun brightening. 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. See Future of the Earth.,
In about 5-6 billion years from now, the Sun will start to become a red giant. The oceans and the much of the atmosphere will boil away and the Earth's temperature will rise well above the boiling point of water. About 7-8 billion years from now, the Earth will probably be engulfed by an expanding Sun and destroyed.,
Further information: Population decline
Preference for fewer children; if developed world demographics are extrapolated they mathematically lead to 'soft' extinction before 3000 CE. (John A. Leslie estimates that if the reproduction rate drops to the German level the extinction date will be 2400.),
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.,
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.,
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.,
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.Gerard O'Neill has cautioned that first contact with alien intelligence may follow the precedent set by historical examples of contact between human civilizations, where the less technologically-advanced civilization has inevitably succumbed to the other civilization, regardless of its intentions.,
A vacuum phase transition could destroy the universe.,
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; 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:
The threat of nuclear annihilation was a significant concern in the lives of many people from the 1950s through the 1980s.
All past predictions of human extinction have proven to be false; to some, this makes future warnings seem less credible. John von Neumann was probably wrong in having "a certainty" that nuclear war would occur. (Of course, our survival is not, in itself, proof that the chance of a fatal nuclear exchange was low, or that such an event could not occur in the future). Others, such as Nick Bostrom, argue that the lack of human extinction in the past is weak evidence that there will be no human extinction in the future, due to survivor bias and other anthropic effects. Bostrom speculates that extinction risk-analysis may be an "overlooked field" because it is both too psychologically troublesome a subject area to be attractive to potential researchers, and because the lack of previous human species extinction events leads a depressed view of the likelihood of it happening under changing future circumstances.
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.
Many people believe humanity's intelligence and sense of self preservation offer safe-guards against extinction. They argue that people will find creative ways to overcome potential threats, and will take care of the precautionary principle in attempting dangerous innovations. Others believe that the management of destructive technology is becoming difficult, and that the precautionary principle is often abandoned whenever the reward appears to outweigh the risk.
Shortly before the Trinity nuclear test, one of the project's lead scientists (Teller) speculated that the fission explosion might destroy New Mexico and possibly the world, by causing a reaction in the nitrogen of the atmosphere. Hans Bethe then calculated that such a reaction was theoretically impossible. It is unknown whether the U.S. would have eventually proceeded with the test anyway, had Bethe calculated a small but nonzero risk of destroying the world.
Observations about human extinction:
Dave Raup and Jack Sepkoski claim there is a mysterious twenty-six-million-year periodicity in elevated extinction rates. Based on past extinction rates, Raup and others infer that the average longevity of a typical vertebrate species is 2-4 million years. However, generalist, geographically dispersed species, like humans, may have a lower rate of extinction than those species that require a particular habitat.
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.
Quantifying the Impact:
Carl Sagan argued:
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.
One scholar argues that any risk of human extinction above 1 in 10 should ethically be considered "unacceptable".
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Omnicide is human extinction as a result of human action. Most commonly it refers to extinction through nuclear warfare or biological warfare, but it can also apply to extinction through means such as global anthropogenic ecological catastrophe.
Omnicide can be considered a subcategory of genocide. Using the concept in this way, one can argue, for example, that:
The arms race is genocidal in intent given the fact that the United States and the Soviet Union are knowingly preparing to destroy each other as viable national and political groups.
This concept of omnicide attempts to raise issues of human agency and moral responsibility in discussions about large-scale social processes like the nuclear arms race. To describe a human extinction scenario as 'omnicidal' is to claim that, if it were to happen, it would result not just from natural, uncontrollable evolutionary forces, or from some random catastrophe like an asteroid impact, but from deliberate choices made by human beings. In this view, such scenarios are preventable, and people whose choices make them more likely to happen should be held morally accountable.
In popular culture:
The book The World Without Us by Alan Weisman deals with a thought experiment on what would happen to the planet and especially human-made infrastructures if humans suddenly disappeared. The Discovery Channel documentary miniseries The Future Is Wild shows the possible future of evolution on Earth without humans. The History Channel's special Life After People examines the possible future of life on Earth without humans, and was made into a series of the same name. The National Geographic Channel's special Aftermath: Population Zero envisions what the world be like if all humans suddenly disappeared. A threat of human extinction drives the plot of innumerable science fiction stories, from When Worlds Collide to 2012. Usually the extinction threat is narrowly avoided, but some exceptions exist, such as R.U.R. and A.I.