Human extinction

Moral importance of existential risk

"Existential risks" are risks that threaten the entire future of humanity, whether by causing human extinction or by otherwise permanently crippling human progress. Many scholars make an argument based on the size of the "cosmic endowment" and state that because of the inconceivably large number of potential future lives that are at stake, even small reductions of existential risk have great value. Some of the arguments run as follows:

Size of the "cosmic endowment"

Parfit argues that, if the Earth is habitable for a billion more years, and if it can sustainably support a population of more than a billion, then there is a potential for 10¹⁶ (or 10,000,000,000,000,000) human lives of normal duration. Bostrom goes further, stating that if the universe is empty, then the accessible universe can support at least 10³⁴ biological human life-years; and, if some humans were uploaded onto computers, could support the equivalent of at least 10⁵⁴ cybernetic human life-years.

Severe forms of known or recorded 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.

Habitat threats

Population decline

Scientific accidents

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. 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 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.

Scenarios of extraterrestrial origin

Evolution

Humans could evolve, through genetic engineering or technological modification, into a new species – posthumans. Commentators such as Kevin Warwick and Ian Pearson point to the possibility of humans evolving by merging with technology. Furthermore, "normal" biological evolution of humanity may continue so that Homo sapiens may gradually transition into one or more new species.

Probability estimates

Because human extinction is unprecedented, speculation about the probability of different scenarios is highly subjective. Astronomer Martin Rees gives humanity a 50-50 chance of extinction during the 21st century, and Nick Bostrom argues that it would be "misguided" to assume that the probability of near-term extinction is less than 25%, and that it will be "a tall order" for the human race to "get our precautions sufficiently right the first time", given that an existential risk provides no opportunity to learn from failure. A little more optimistically, philosopher John Leslie assigns a 70% chance of humanity surviving the next five centuries, based partly on the controversial philosophical doomsday argument that Leslie champions. The 2006 Stern Review for the UK Treasury assumes the 100-year probability of human extinction is 10% in its economic calculations.

Some scholars believe that certain scenarios such as global thermonuclear war would have difficulty eradicating every last settlement on Earth. Physicist Willard Wells points out that any credible extinction scenario would have to reach into a diverse set of areas, including the underground subways of major cities, the mountains of Tibet, the remotest islands of the South Pacific, and even to McMurdo Station in Antarctica, which has contigency plans and supplies for a long isolation. In addition, elaborate bunkers exist for government leaders to occupy during a nuclear war. Any number of events could lead to a massive loss of human life; but if the last few, most resilient, humans are unlikely to also die off, then that particular human extinction scenario is not credible.

Psychology

Eliezer Yudkowsky theorizes that scope neglect plays a role in public perception of existential risks:

Substantially larger numbers, such as 500 million deaths, and especially qualitatively different scenarios such as the extinction of the entire human species, seem to trigger a different mode of thinking... People who would never dream of hurting a child hear of an existential risk, and say, "Well, maybe the human species doesn't really deserve to survive".

All past predictions of human extinction have proven to be false; to some, this makes future warnings seem less credible. Nick Bostrom argues 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.

Research and initiatives

Even though the importance and potential impact of research on existential risks is often highlighted relatively few research-efforts are being made in this field. In 2001 Bostrom stated:

However, multiple organizations with the goal of helping prevent human extinction have been founded, such as the Future of Humanity Institute, the Centre for the Study of Existential Risk, the Future of Life Institute, the Machine Intelligence Research Institute and the Global Catastrophic Risk Institute.

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.^[3]

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.^[4]

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.

The threat of nuclear annihilation was a significant concern in the lives of many people from the 1950s through the 1980s.

Observations about human extinction

David M. Raup and Jack Sepkoski claim there is a mysterious 26 million-year periodicity in elevated extinction rates.

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 100,000 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, 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 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, effect the climate in various ways in either extreme cold or extreme heat.

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.

Omnicide

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:

Proposed countermeasures

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 from planet-wide events such as global thermonuclear war.

More economically, some scholars propose the establishment on Earth of one or more self-sufficient, remote, permanently occupied settlements specifically created for the purpose of surviving global disaster. Economist Robin Hanson argues that a refuge permanently housing as few as 100 people would significantly improve the chances of human survival during a range of global catastrophes.

In popular culture

Some 21st century pop-science works, including The World Without Us by Alan Weisman, pose an artistic thought experiment: what would happen to the rest of the planet if humans suddenly disappeared? A threat of human extinction drives the plot of innumerable science fiction stories; an influential early example is the 1951 film adaption of When Worlds Collide. Usually the extinction threat is narrowly avoided, but some exceptions exist, such as R.U.R. and Steven Spielberg's A.I.