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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, pandemic 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, overpopulation or global accidental pandemic; besides natural ones: bolide impact and large scale volcanism or other catastrophic climate change. These natural causes 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 actually 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.
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Overpopulation leads to higher risk of famine due to the increasing need for centralized agriculture with a lack of biodiversity. A single staple crop getting a disease or pest attack could lead to mass food crisis. The transition from fossil fuel chemical based agriculture to future alternatives such as organic agriculture will be a more risky transition with a high population. The world currently uses around 40% of its land mass for agriculture and almost all of its arable land. Overpopulation also puts a strain on the environment and natural resources that are in many ways relied upon for survival.
Attitudes to human extinction vary widely depending on beliefs concerning spiritual survival (souls, heaven, reincarnation, and so forth), the value of the human species, whether the human species evolves individually or collectively, and many other factors. Many religions prophesy an "end times" to the universe. Human extinction is therefore a part of the faith of many humans to the extent that the end time means the absolute end of their physical humanity but perhaps not an eternal soul.
However not all faiths connect human extinction to the end times, since some believe in cyclical regeneration, or that end times actually means the beginning of a new kind of existence (see eschatology and utopianism).
The general level of fear about human extinction, in the near term, is very low, despite the pronouncements of some fringe groups. It is not an outcome considered by many as a credible risk. Suggested reasons for human extinction's low public visibility:
In general, humanity's sense of self preservation, and intelligence are considered to offer safe-guards against extinction. It is felt that people will find creative ways to overcome potential threats, and will take care of the precautionary principle in attempting dangerous innovations. The arguments against this are; firstly, that the management of destructive technology is becoming difficult, and secondly, that the precautionary principle is often abandoned whenever the reward appears to outweigh the risk. At least one instance where the principle may have been overruled was when prior to the Trinity nuclear test, one of the project's 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. A calculation by Hans Bethe proved such a possibility theoretically impossible, but the fear of the possibility remained among some until the test took place.
The fact that the vast majority of the species that have existed on Earth have become extinct, has led to the suggestion that all species have a finite lifespan and thus human extinction would be inevitable. Dave Raup and Jack Sepkoski found for example a twenty-six-million-year periodicity in elevated extinction rates, caused by factors unknown (See David M. Raup. "Extinction: Bad Genes or Bad Luck" (1992, Norton). Based upon evidence of past extinction rates Raup and others have suggested that the average longevity of an invertebrate species is between 4-6 million years, while that of vertebrates seems to be 2-4 million years. The shorter period of survival for mammals lies in their position further up the food chain than many invertebrates, and therefore an increased liability to suffer the effects of environmental change. A counter-argument to this is that humans are unique in their adaptive and technological capabilities, so it is not possible to draw reliable inferences about the probability of human extinction based on the past extinctions of other species. Certainly, the evidence collected by Raup and others suggested that generalist, geographically dispersed species, like humans, generally have a lower rate of extinction than those species that require a particular habitat. In addition, the human species is probably the only species with a conscious prior knowledge of their own demise, and therefore would be likely to take steps to avoid it.
Humans are very similar to other primates in their propensity towards intra-species violence; Jared Diamond's The Third Chimpanzee (ISBN 0-09-980180-9) estimates that 64% of hunter-gather societies engage in warfare every two years. Although it has been argued (e.g. in the UNESCO Seville Statement) that warfare is a cultural artifact, many anthropologists dispute this, noting that small human tribes exhibit similar patterns of violence to chimpanzee groups, the most murderous of the primates, and one of two of our nearest living genetic relatives. The "higher" functions of reason and speech are more developed in the brain of Homo sapiens than other primates, but the relative size of the limbic system is a constant in apes, monkeys and humans. The combination of inventiveness and urge to violence in humans has been cited as evidence against its long term survival.
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.
|“||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.||”|
As this claim illustrates, the concept of omnicide raises issues of human agency and, hence, of moral responsibility in discussions about large-scale social processes like the nuclear arms race or ecologically destructive industrial production. That is, part of the point of describing a human extinction scenario as 'omnicidal' is to note 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. This implies that such scenarios are preventable, and that the people whose choices make them more likely to happen should be held morally accountable for such choices. In this context, the label 'omnicide' also works to de-normalize the course of action it is applied to.
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. The British science-fiction drama Primeval also puts forward an alternative view of Earth after the extinction of humans: how other species of animals, such as rodents and insects will evolve to fill niches left by humans.
^ Von Neumann said it was "absolutely certain (1) that there would be a nuclear war; and (2) that everyone would die in it" (underline added to quote from: The Nature of the Physical Universe – 1979, John Wiley & Sons, ISBN 0-471-03190-9, in H. Putnam’s essay The place of facts in a world of values - page 113). This example illustrates why respectable scientists are very reluctant to go on record with extinction predictions: they can never be proven right. (The quotation is repeated by Leslie (1996) on page 26, on the subject of nuclear war annihilation, which he still considered a significant risk – in the mid 1990s.)
^ Although existential risks are less manageable by individuals than health risks, according to Ken Olum, Joshua Knobe, and Alexander Vilenkin the possibility of human extinction does have practical implications. For instance, if the “universal” Doomsday argument is accepted it changes the most likely source of disasters, and hence the most efficient means of preventing them. They write: "...you should be more concerned that a large number of asteroids have not yet been detected than about the particular orbit of each one. You should not worry especially about the chance that some specific nearby star will become a supernova, but more about the chance that supernovas are more deadly to nearby life then we believe." Source: “Practical application” page 39 of the Princeton University paper: Philosophical Implications of Inflationary Cosmology
^ The 2000 review Armageddon at the Millennial Dawn from The Journal of Religion and Film finds that "While end of the world threats perhaps are not avoidable, the cinematic formulation of millennial doom promotes the notion that the end can be averted through employing human ingenuity, scientific advance, and heroism." Since this review was conducted, there had been a Hollywood production which postulates a (far future) outcome where humans are extinct (at least in the wild): A.I..
^ For research on this, see Psychological science volume 15 (2004): Decisions From Experience and the Effect of Rare Events in Risky Choice. The under-perception of rare events mentioned above is actually the opposite of the phenomenon originally described by Kahneman in "prospect theory" (in their original experiments the likelihood of rare events is overestimated). However, further analysis of the bias has shown that both forms occur: When judging from description people tend to overestimate the described probability, so this effect taken alone would indicate that reading the extinction scenarios described here should make the reader overestimate the likelihood of any probabilities given. However, the effect that is more relevant to common consideration of human extinction is the bias that occurs with estimates from experience, and these are in the opposite direction: When judging from personal experience people who have never heard of or experienced their species become extinct would be expected to dramatically underestimate its likelihood. Sociobiologist E. O. Wilson argued that: "The reason for this myopic fog, evolutionary biologists contend, is that it was actually advantageous during all but the last few millennia of the two million years of existence of the genus Homo... A premium was placed on close attention to the near future and early reproduction, and little else. Disasters of a magnitude that occur only once every few centuries were forgotten or transmuted into myth." (Is Humanity Suicidal? New York Times Magazine May 30, 1993).
^ Abrupt.org 1996 editorial lists (and condemns) the arguments for human’s tendency to self-destruction. In this view, the history of humanity suggests that humans will be the cause of their own extinction. However, others have reached the opposite conclusion with the same data on violence and hypothesize that as societies develop armies and weapons with greater destructive power, they tend to be used less often. It is claimed that this implies a more secure future, despite the development of WMD technology. As such this argument may constitute a form of deterrence theory. Counter-arguments against such views include the following: (1) All weapons ever designed have ultimately been used. States with strong military forces tend to engage in military aggression, (2) Although modern states have so far generally shown restraint in unleashing their most potent weapons, whatever rational control was guaranteed by government monopoly over such weapons becomes increasingly irrelevant in a world where individuals have access to the technology of mass destruction (as proposed in Our Final Hour, for example).
^ ReligiousTolerance.org says that Aum Supreme Truth is the only religion known to have planned Armageddon for non-believers. Their intention to unleash deadly viruses is covered in Our Final Hour, and by Aum watcher, Akihiko Misawa. The Gaia Liberation Front advocates (but is not known to have active plans for) total human genocide, see: GLF, A Modest Proposal. Leslie, 1996 says that Aum’s collection of nuclear physicists presented a doomsday threat from nuclear destruction as well, especially as the cult included a rocket scientist.
^ Leslie (1996) discusses the survivorship bias (which he calls an "observational selection" effect on page 139) he says that the a priori certainty of observing an "undisasterous past" could make it difficult to argue that we must be safe because nothing terrible has yet occurred. He quotes Holger Bech Nielsen’s formulation: “We do not even know if there should exist some extremely dangerous decay of say the proton which caused eradication of the earth, because if it happens we would no longer be there to observe it and if it does not happen there is nothing to observe.” (From: Random dynamics and relations between the number of fermion generations and the fine structure constants, Acta Pysica Polonica B, May 1989).
^ For example, in the essay Why the future doesn't need us, computer scientist Bill Joy argued that human beings are likely to guarantee their own extinction through transhumanism. See: Wired archive, Why the future doesn't need us.
^ For the “West Germany” extrapolation see: Leslie, 1996 (The End of the World) in the “War, Pollution, and disease” chapter (page 74). In this section the author also mentions the success (in lowering the birth rate) of programs such as the sterilization-for-rupees programs in India, and surveys other infertility or falling birth-rate extinciton scenarios. He says that the voluntary small family behaviour may be counter-evolutionary, but that the meme for small, rich families appears to be spreading rapidly throughout the world. In 2150 the world population is expected to start falling.
^ See estimate of contact’s probability at galactic-guide. Former NASA consultant David Brin's lengthy rebuttal to SETI enthusiast's optimism about alien intentions concludes: "The worst mistake of first contact, made throughout history by individuals on both sides of every new encounter, has been the unfortunate habit of making assumptions. It often proved fatal." (See full text at SETIleague.org.)