Human extinction
Human extinction or omnicide is the end of the human species, either by population decline due to extraneous natural causes, such as an asteroid impact or large-scale volcanism, or via anthropogenic destruction.
Some of the many possible contributors to anthropogenic hazards are climate change, global nuclear annihilation, biological warfare, weapons of mass destruction, and ecological collapse. Other scenarios center on emerging technologies, such as advanced artificial intelligence, biotechnology, or self-replicating nanobots.
The scientific consensus is that there is a relatively low risk of near-term human extinction due to natural causes. The likelihood of human extinction through humankind's own activities, however, is a current area of research and debate.
History of thought
Early history
Before the 18th and 19th centuries, the possibility that humans or other organisms could become extinct was viewed with scepticism. It contradicted the principle of plenitude, a doctrine that all possible things exist. The principle traces back to Aristotle and was an important tenet of Christian theology. Ancient philosophers such as Plato, Aristotle, and Lucretius wrote of the end of humankind only as part of a cycle of renewal. Marcion of Sinope was a proto-Protestant who advocated for antinatalism that could lead to human extinction. Later philosophers such as Al-Ghazali, William of Ockham, and Gerolamo Cardano expanded the study of logic and probability and began wondering if abstract worlds existed, including a world without humans. Physicist Edmond Halley stated that the extinction of the human race may be beneficial to the future of the world.The notion that species can become extinct gained scientific acceptance during the Age of Enlightenment in the 17th and 18th centuries, and by 1800 Georges Cuvier had identified 23 extinct prehistoric species. The doctrine was further gradually bolstered by evidence from the natural sciences, particularly the discovery of fossil evidence of species that appeared to no longer exist and the development of theories of evolution. In On the Origin of Species, Charles Darwin discussed the extinction of species as a natural process and a core component of natural selection. Notably, Darwin was skeptical of the possibility of sudden extinction, viewing it as a gradual process. He held that the abrupt disappearances of species from the fossil record were not evidence of catastrophic extinctions but rather represented unrecognized gaps in the record.
As the possibility of extinction became more widely established in the sciences, so did the prospect of human extinction. In the 19th century, human extinction became a popular topic in science and fiction. In 1863, a few years after Darwin published On the Origin of Species, William King proposed that Neanderthals were an extinct species of the genus Homo. The Romantic authors and poets were particularly interested in the topic. Lord Byron wrote about the extinction of life on Earth in his 1816 poem "Darkness," and in 1824 envisaged humanity being threatened by a comet impact and employing a missile system to defend against it. Mary Shelley's 1826 novel The Last Man is set in a world where humanity has been nearly destroyed by a mysterious plague. At the turn of the 20th century, Russian cosmism, a precursor to modern transhumanism, advocated avoiding humanity's extinction by colonizing space.
Atomic era
The invention of the atomic bomb prompted a wave of discussion among scientists, intellectuals, and the public at large about the risk of human extinction. In a 1945 essay, Bertrand Russell wrote:The prospect for the human race is sombre beyond all precedent. Mankind are faced with a clear-cut alternative: either we shall all perish, or we shall have to acquire some slight degree of common sense.In 1950, Leo Szilard suggested it was technologically feasible to build a cobalt bomb that could render the planet unlivable. A 1950 Gallup poll found that 19% of Americans believed that another world war would mean "an end to mankind". Rachel Carson's 1962 book Silent Spring raised awareness of environmental catastrophe. In 1983, Brandon Carter proposed the Doomsday argument, which used Bayesian probability to predict the total number of humans that will ever exist.
The discovery of "nuclear winter" in the early 1980s, a specific mechanism by which nuclear war could result in human extinction, again raised the issue to prominence. Writing about these findings in 1983, Carl Sagan argued that measuring the severity of extinction solely in terms of those who die "conceals its full impact," and that nuclear war "imperils all of our descendants, for as long as there will be humans."
Post-Cold War
's 1996 book The End of the World was an academic treatment of the science and ethics of human extinction. In it, Leslie considered a range of threats to humanity and what they have in common. In 2003, British Astronomer Royal Sir Martin Rees published Our Final Hour, in which he argues that advances in certain technologies create new threats to the survival of humankind and that the 21st century may be a critical moment in history when humanity's fate is decided. Edited by Nick Bostrom and Milan M. Ćirković, Global Catastrophic Risks, published in 2008, is a collection of essays from 26 academics on various global catastrophic and existential risks. Nicholas P. Money's 2019 book The Selfish Ape delves into the environmental consequences of overexploitation. Toby Ord's 2020 book The Precipice argues that preventing existential risks is one of the most important moral issues of our time. The book discusses, quantifies, and compares different existential risks, concluding that the greatest risks are presented by unaligned artificial intelligence and biotechnology. Lyle Lewis' 2024 book Racing to Extinction explores the roots of human extinction from an evolutionary biology perspective. Lewis argues that humanity treats unused natural resources as waste and is driving ecological destruction through overexploitation, habitat loss, and denial of environmental limits. He uses vivid examples, like the extinction of the passenger pigeon and the environmental cost of rice production, to show how interconnected and fragile ecosystems are.Causes
Potential anthropogenic causes of human extinction include global thermonuclear war, deployment of a highly effective biological weapon, ecological collapse, runaway artificial intelligence, runaway nanotechnology, overpopulation and increased consumption causing resource depletion and a concomitant population crash, population decline by choosing to have fewer children, and displacement of naturally evolved humans by a new species produced by genetic engineering or technological augmentation. Natural and external extinction risks include high-fatality-rate pandemic, supervolcanic eruption, asteroid impact, nearby supernova or gamma-ray burst, or extreme solar flare.Humans as a species may also be considered to have "gone extinct" simply by being replaced with distant descendants whose continued evolution may produce new species or subspecies of Homo or of hominids.
Without intervention from unforeseen forces, the stellar evolution of the Sun is expected to render Earth uninhabitable and ultimately lead to its destruction. The entire universe may eventually become uninhabitable, depending on its ultimate fate and the processes that govern it.
Probability
Natural vs. anthropogenic
Experts generally agree that anthropogenic existential risks are more likely than natural risks. A key difference between these risk types is that empirical evidence can place an upper bound on the level of natural risk. Humanity has existed for at least 200,000 years, over which it has been subject to a roughly constant level of natural risk. If the natural risk were high enough, humanity wouldn't have survived this long. Based on a formalization of this argument, researchers have concluded that we can be confident that natural risk is lower than 1 in 14,000 per year.Another empirical method to study the likelihood of certain natural risks is to investigate the geological record. For example, a comet or asteroid impact event sufficient in scale to cause an impact winter that would cause human extinction before the year 2100 has been estimated at one in a million. Moreover, large supervolcano eruptions may cause a volcanic winter that could endanger the survival of humanity. The geological record suggests that supervolcanic eruptions are estimated to occur on average about once every 50,000 years, though most such eruptions would not reach the scale required to cause human extinction. Famously, the supervolcano Mt. Toba may have almost wiped out humanity at the time of its last eruption.
Since anthropogenic risk is a relatively recent phenomenon, humanity's track record of survival cannot provide similar assurances. Humanity has only existed for 80 years since the creation of nuclear weapons, and there is no historical track record for future technologies. This has led thinkers like Carl Sagan to conclude that humanity is currently in a "time of perils," a uniquely dangerous period in human history, where it is subject to unprecedented levels of risk, beginning from when humans first started posing risk to themselves through their actions. Paleobiologist Olev Vinn has suggested that humans presumably have a number of inherited behavior patterns that are not fine-tuned for conditions prevailing in technological civilization. Some IBPs may be highly incompatible with such conditions and have a high potential to induce self-destruction. These patterns may include responses of individuals seeking power over conspecifics in relation to harvesting and consuming energy. Nonetheless, there are ways to address the issue of inherited behavior patterns.