Extinction

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"Extinct" redirects here. Extinction_sentence_0

For other uses, see Extinct (disambiguation) and Extinction (disambiguation). Extinction_sentence_1

Extinction_table_infobox_0

Conservation status by IUCN Red List categoryExtinction_header_cell_0_0_0
ExtinctExtinction_header_cell_0_1_0
Extinction_header_cell_0_2_0 Extinction_cell_0_2_1
ThreatenedExtinction_header_cell_0_3_0
Extinction_header_cell_0_4_0 Extinction_cell_0_4_1
Lower RiskExtinction_header_cell_0_5_0
Extinction_header_cell_0_6_0 Extinction_cell_0_6_1
Extinction_header_cell_0_7_0 Extinction_cell_0_7_1

Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. Extinction_sentence_2

The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point. Extinction_sentence_3

Because a species' potential range may be very large, determining this moment is difficult, and is usually done retrospectively. Extinction_sentence_4

This difficulty leads to phenomena such as Lazarus taxa, where a species presumed extinct abruptly "reappears" (typically in the fossil record) after a period of apparent absence. Extinction_sentence_5

More than 99% of all species that ever lived on Earth, amounting to over five billion species, are estimated to have died out. Extinction_sentence_6

It is estimated that there are currently around 8.7 million species of eukaryote globally, and possibly many times more if microorganisms, like bacteria, are included. Extinction_sentence_7

Notable extinct animal species include non-avian dinosaurs, saber-toothed cats, dodos, mammoths, ground sloths, thylacines, trilobites and golden toads. Extinction_sentence_8

Through evolution, species arise through the process of speciation—where new varieties of organisms arise and thrive when they are able to find and exploit an ecological niche—and species become extinct when they are no longer able to survive in changing conditions or against superior competition. Extinction_sentence_9

The relationship between animals and their ecological niches has been firmly established. Extinction_sentence_10

A typical species becomes extinct within 10 million years of its first appearance, although some species, called living fossils, survive with little to no morphological change for hundreds of millions of years. Extinction_sentence_11

Mass extinctions are relatively rare events; however, isolated extinctions are quite common. Extinction_sentence_12

Only recently have extinctions been recorded and scientists have become alarmed at the current high rate of extinctions. Extinction_sentence_13

Most species that become extinct are never scientifically documented. Extinction_sentence_14

Some scientists estimate that up to half of presently existing plant and animal species may become extinct by 2100. Extinction_sentence_15

A 2018 report indicated that the phylogenetic diversity of 300 mammalian species erased during the human era since the Late Pleistocene would require 5 to 7 million years to recover. Extinction_sentence_16

According to the 2019 Global Assessment Report on Biodiversity and Ecosystem Services by IPBES, the biomass of wild mammals has fallen by 82%, natural ecosystems have lost about half their area and a million species are at risk of extinction—all largely as a result of human actions. Extinction_sentence_17

Twenty-five percent of plant and animal species are threatened with extinction. Extinction_sentence_18

In June 2019, one million species of plants and animals were at risk of extinction. Extinction_sentence_19

At least 571 species are lost since 1750 but likely many more. Extinction_sentence_20

The main cause of the extinctions is the destruction of natural habitats by human activities, such as cutting down forests and converting land into fields for farming. Extinction_sentence_21

A dagger symbol (†) placed next to the name of a species or other taxon normally indicates its status as extinct. Extinction_sentence_22

Definition Extinction_section_0

A species is extinct when the last existing member dies. Extinction_sentence_23

Extinction therefore becomes a certainty when there are no surviving individuals that can reproduce and create a new generation. Extinction_sentence_24

A species may become functionally extinct when only a handful of individuals survive, which cannot reproduce due to poor health, age, sparse distribution over a large range, a lack of individuals of both sexes (in sexually reproducing species), or other reasons. Extinction_sentence_25

Pinpointing the extinction (or pseudoextinction) of a species requires a clear definition of that species. Extinction_sentence_26

If it is to be declared extinct, the species in question must be uniquely distinguishable from any ancestor or daughter species, and from any other closely related species. Extinction_sentence_27

Extinction of a species (or replacement by a daughter species) plays a key role in the punctuated equilibrium hypothesis of Stephen Jay Gould and Niles Eldredge. Extinction_sentence_28

In ecology, extinction is often used informally to refer to local extinction, in which a species ceases to exist in the chosen area of study, but may still exist elsewhere. Extinction_sentence_29

This phenomenon is also known as extirpation. Extinction_sentence_30

Local extinctions may be followed by a replacement of the species taken from other locations; wolf reintroduction is an example of this. Extinction_sentence_31

Species which are not extinct are termed extant. Extinction_sentence_32

Those that are extant but threatened by extinction are referred to as threatened or endangered species. Extinction_sentence_33

Currently an important aspect of extinction is human attempts to preserve critically endangered species. Extinction_sentence_34

These are reflected by the creation of the conservation status "extinct in the wild" (EW). Extinction_sentence_35

Species listed under this status by the International Union for Conservation of Nature (IUCN) are not known to have any living specimens in the wild, and are maintained only in zoos or other artificial environments. Extinction_sentence_36

Some of these species are functionally extinct, as they are no longer part of their natural habitat and it is unlikely the species will ever be restored to the wild. Extinction_sentence_37

When possible, modern zoological institutions try to maintain a viable population for species preservation and possible future reintroduction to the wild, through use of carefully planned breeding programs. Extinction_sentence_38

The extinction of one species' wild population can have knock-on effects, causing further extinctions. Extinction_sentence_39

These are also called "chains of extinction". Extinction_sentence_40

This is especially common with extinction of keystone species. Extinction_sentence_41

A 2018 study indicated that the sixth mass extinction started in the Late Pleistocene could take up to 5 to 7 million years to restore 2.5 billion years of unique mammal diversity to what it was before the human era. Extinction_sentence_42

Pseudoextinction Extinction_section_1

Main article: Pseudoextinction Extinction_sentence_43

Extinction of a parent species where daughter species or subspecies are still extant is called pseudoextinction or phyletic extinction. Extinction_sentence_44

Effectively, the old taxon vanishes, transformed (anagenesis) into a successor, or split into more than one (cladogenesis). Extinction_sentence_45

Pseudoextinction is difficult to demonstrate unless one has a strong chain of evidence linking a living species to members of a pre-existing species. Extinction_sentence_46

For example, it is sometimes claimed that the extinct Hyracotherium, which was an early horse that shares a common ancestor with the modern horse, is pseudoextinct, rather than extinct, because there are several extant species of Equus, including zebra and donkey; however, as fossil species typically leave no genetic material behind, one cannot say whether Hyracotherium evolved into more modern horse species or merely evolved from a common ancestor with modern horses. Extinction_sentence_47

Pseudoextinction is much easier to demonstrate for larger taxonomic groups. Extinction_sentence_48

Lazarus taxa Extinction_section_2

Main article: Lazarus taxa Extinction_sentence_49

The coelacanth, a fish related to lungfish and tetrapods, was considered to have been extinct since the end of the Cretaceous Period. Extinction_sentence_50

In 1938, however, a living specimen was found off the Chalumna River (now Tyolomnqa) on the east coast of South Africa. Extinction_sentence_51

Museum curator Marjorie Courtenay-Latimer discovered the fish among the catch of a local trawler operated by Captain Hendrick Goosen, on December 23, 1938. Extinction_sentence_52

A local chemistry professor, JLB Smith, confirmed the fish's importance with a famous cable: "MOST IMPORTANT PRESERVE SKELETON AND GILLS = FISH DESCRIBED". Extinction_sentence_53

Far more recent possible or presumed extinctions of species which may turn out still to exist include the thylacine, or Tasmanian tiger (Thylacinus cynocephalus), the last known example of which died in Hobart Zoo in Tasmania in 1936; the Japanese wolf (Canis lupus hodophilax), last sighted over 100 years ago; the American ivory-billed woodpecker (Campephilus principalis), with the last universally accepted sighting in 1944; and the slender-billed curlew (Numenius tenuirostris), not seen since 2007. Extinction_sentence_54

Causes Extinction_section_3

As long as species have been evolving, species have been going extinct. Extinction_sentence_55

It is estimated that over 99.9% of all species that ever lived are extinct. Extinction_sentence_56

The average lifespan of a species is 1–10 million years, although this varies widely between taxa. Extinction_sentence_57

There are a variety of causes that can contribute directly or indirectly to the extinction of a species or group of species. Extinction_sentence_58

"Just as each species is unique", write Beverly and Stephen C. Stearns, "so is each extinction ... the causes for each are varied—some subtle and complex, others obvious and simple". Extinction_sentence_59

Most simply, any species that cannot survive and reproduce in its environment and cannot move to a new environment where it can do so, dies out and becomes extinct. Extinction_sentence_60

Extinction of a species may come suddenly when an otherwise healthy species is wiped out completely, as when toxic pollution renders its entire habitat unliveable; or may occur gradually over thousands or millions of years, such as when a species gradually loses out in competition for food to better adapted competitors. Extinction_sentence_61

Extinction may occur a long time after the events that set it in motion, a phenomenon known as extinction debt. Extinction_sentence_62

Assessing the relative importance of genetic factors compared to environmental ones as the causes of extinction has been compared to the debate on nature and nurture. Extinction_sentence_63

The question of whether more extinctions in the fossil record have been caused by evolution or by catastrophe is a subject of discussion; Mark Newman, the author of Modeling Extinction, argues for a mathematical model that falls between the two positions. Extinction_sentence_64

By contrast, conservation biology uses the extinction vortex model to classify extinctions by cause. Extinction_sentence_65

When concerns about human extinction have been raised, for example in Sir Martin Rees' 2003 book Our Final Hour, those concerns lie with the effects of climate change or technological disaster. Extinction_sentence_66

Currently, environmental groups and some governments are concerned with the extinction of species caused by humanity, and they try to prevent further extinctions through a variety of conservation programs. Extinction_sentence_67

Humans can cause extinction of a species through overharvesting, pollution, habitat destruction, introduction of invasive species (such as new predators and food competitors), overhunting, and other influences. Extinction_sentence_68

Explosive, unsustainable human population growth and increasing per capita consumption are essential drivers of the extinction crisis. Extinction_sentence_69

According to the International Union for Conservation of Nature (IUCN), 784 extinctions have been recorded since the year 1500, the arbitrary date selected to define "recent" extinctions, up to the year 2004; with many more likely to have gone unnoticed. Extinction_sentence_70

Several species have also been listed as extinct since 2004. Extinction_sentence_71

Genetics and demographic phenomena Extinction_section_4

See also: Extinction vortex, Genetic erosion, and Mutational meltdown Extinction_sentence_72

If adaptation increasing population fitness is slower than environmental degradation plus the accumulation of slightly deleterious mutations, then a population will go extinct. Extinction_sentence_73

Smaller populations have fewer beneficial mutations entering the population each generation, slowing adaptation. Extinction_sentence_74

It is also easier for slightly deleterious mutations to fix in small populations; the resulting positive feedback loop between small population size and low fitness can cause mutational meltdown. Extinction_sentence_75

Limited geographic range is the most important determinant of genus extinction at background rates but becomes increasingly irrelevant as mass extinction arises. Extinction_sentence_76

Limited geographic range is a cause both of small population size and of greater vulnerability to local environmental catastrophes. Extinction_sentence_77

Extinction rates can be affected not just by population size, but by any factor that affects evolvability, including balancing selection, cryptic genetic variation, phenotypic plasticity, and robustness. Extinction_sentence_78

A diverse or deep gene pool gives a population a higher chance in the short term of surviving an adverse change in conditions. Extinction_sentence_79

Effects that cause or reward a loss in genetic diversity can increase the chances of extinction of a species. Extinction_sentence_80

Population bottlenecks can dramatically reduce genetic diversity by severely limiting the number of reproducing individuals and make inbreeding more frequent. Extinction_sentence_81

Genetic pollution Extinction_section_5

Main article: Genetic pollution Extinction_sentence_82

Extinction can threaten species evolved to specific ecologies through the process of genetic pollution—i.e., uncontrolled hybridization, introgression genetic swamping which leads to homogenization or out-competition from the introduced (or hybrid) species. Extinction_sentence_83

Endemic populations can face such extinctions when new populations are imported or selectively bred by people, or when habitat modification brings previously isolated species into contact. Extinction_sentence_84

Extinction is likeliest for rare species coming into contact with more abundant ones; interbreeding can swamp the rarer gene pool and create hybrids, depleting the purebred gene pool (for example, the endangered wild water buffalo is most threatened with extinction by genetic pollution from the abundant domestic water buffalo). Extinction_sentence_85

Such extinctions are not always apparent from morphological (non-genetic) observations. Extinction_sentence_86

Some degree of gene flow is a normal evolutionarily process, nevertheless, hybridization (with or without introgression) threatens rare species' existence. Extinction_sentence_87

The gene pool of a species or a population is the variety of genetic information in its living members. Extinction_sentence_88

A large gene pool (extensive genetic diversity) is associated with robust populations that can survive bouts of intense selection. Extinction_sentence_89

Meanwhile, low genetic diversity (see inbreeding and population bottlenecks) reduces the range of adaptions possible. Extinction_sentence_90

Replacing native with alien genes narrows genetic diversity within the original population, thereby increasing the chance of extinction. Extinction_sentence_91

Habitat degradation Extinction_section_6

Main article: Habitat destruction Extinction_sentence_92

Habitat degradation is currently the main anthropogenic cause of species extinctions. Extinction_sentence_93

The main cause of habitat degradation worldwide is agriculture, with urban sprawl, logging, mining and some fishing practices close behind. Extinction_sentence_94

The degradation of a species' habitat may alter the fitness landscape to such an extent that the species is no longer able to survive and becomes extinct. Extinction_sentence_95

This may occur by direct effects, such as the environment becoming toxic, or indirectly, by limiting a species' ability to compete effectively for diminished resources or against new competitor species. Extinction_sentence_96

Habitat degradation through toxicity can kill off a species very rapidly, by killing all living members through contamination or sterilizing them. Extinction_sentence_97

It can also occur over longer periods at lower toxicity levels by affecting life span, reproductive capacity, or competitiveness. Extinction_sentence_98

Habitat degradation can also take the form of a physical destruction of niche habitats. Extinction_sentence_99

The widespread destruction of tropical rainforests and replacement with open pastureland is widely cited as an example of this; elimination of the dense forest eliminated the infrastructure needed by many species to survive. Extinction_sentence_100

For example, a fern that depends on dense shade for protection from direct sunlight can no longer survive without forest to shelter it. Extinction_sentence_101

Another example is the destruction of ocean floors by bottom trawling. Extinction_sentence_102

Diminished resources or introduction of new competitor species also often accompany habitat degradation. Extinction_sentence_103

Global warming has allowed some species to expand their range, bringing unwelcome competition to other species that previously occupied that area. Extinction_sentence_104

Sometimes these new competitors are predators and directly affect prey species, while at other times they may merely outcompete vulnerable species for limited resources. Extinction_sentence_105

Vital resources including water and food can also be limited during habitat degradation, leading to extinction. Extinction_sentence_106

Predation, competition, and disease Extinction_section_7

See also: Island restoration Extinction_sentence_107

In the natural course of events, species become extinct for a number of reasons, including but not limited to: extinction of a necessary host, prey or pollinator, inter-species competition, inability to deal with evolving diseases and changing environmental conditions (particularly sudden changes) which can act to introduce novel predators, or to remove prey. Extinction_sentence_108

Recently in geological time, humans have become an additional cause of extinction (some people would say premature extinction) of some species, either as a new mega-predator or by transporting animals and plants from one part of the world to another. Extinction_sentence_109

Such introductions have been occurring for thousands of years, sometimes intentionally (e.g. livestock released by sailors on islands as a future source of food) and sometimes accidentally (e.g. rats escaping from boats). Extinction_sentence_110

In most cases, the introductions are unsuccessful, but when an invasive alien species does become established, the consequences can be catastrophic. Extinction_sentence_111

Invasive alien species can affect native species directly by eating them, competing with them, and introducing pathogens or parasites that sicken or kill them; or indirectly by destroying or degrading their habitat. Extinction_sentence_112

Human populations may themselves act as invasive predators. Extinction_sentence_113

According to the "overkill hypothesis", the swift extinction of the megafauna in areas such as Australia (40,000 years before present), North and South America (12,000 years before present), Madagascar, Hawaii (AD 300–1000), and New Zealand (AD 1300–1500), resulted from the sudden introduction of human beings to environments full of animals that had never seen them before, and were therefore completely unadapted to their predation techniques. Extinction_sentence_114

Coextinction Extinction_section_8

Main article: Coextinction Extinction_sentence_115

Coextinction refers to the loss of a species due to the extinction of another; for example, the extinction of parasitic insects following the loss of their hosts. Extinction_sentence_116

Coextinction can also occur when a species loses its pollinator, or to predators in a food chain who lose their prey. Extinction_sentence_117

"Species coextinction is a manifestation of one of the interconnectedness of organisms in complex ecosystems ... Extinction_sentence_118

While coextinction may not be the most important cause of species extinctions, it is certainly an insidious one". Extinction_sentence_119

Coextinction is especially common when a keystone species goes extinct. Extinction_sentence_120

Models suggest that coextinction is the most common form of biodiversity loss. Extinction_sentence_121

There may be a cascade of coextinction across the trophic levels. Extinction_sentence_122

Such effects are most severe in mutualistic and parasitic relationships. Extinction_sentence_123

An example of coextinction is the Haast's eagle and the moa: the Haast's eagle was a predator that became extinct because its food source became extinct. Extinction_sentence_124

The moa were several species of flightless birds that were a food source for the Haast's eagle. Extinction_sentence_125

Climate change Extinction_section_9

Main article: Extinction risk from global warming Extinction_sentence_126

See also: Effect of climate change on plant biodiversity, Effects of climate change on terrestrial animals, and Effects of climate change on marine mammals Extinction_sentence_127

Extinction as a result of climate change has been confirmed by fossil studies. Extinction_sentence_128

Particularly, the extinction of amphibians during the Carboniferous Rainforest Collapse, 305 million years ago. Extinction_sentence_129

A 2003 review across 14 biodiversity research centers predicted that, because of climate change, 15–37% of land species would be "committed to extinction" by 2050. Extinction_sentence_130

The ecologically rich areas that would potentially suffer the heaviest losses include the Cape Floristic Region, and the Caribbean Basin. Extinction_sentence_131

These areas might see a doubling of present carbon dioxide levels and rising temperatures that could eliminate 56,000 plant and 3,700 animal species. Extinction_sentence_132

Climate change has also been found to be a factor in habitat loss and desertification. Extinction_sentence_133

Mass extinctions Extinction_section_10

Main article: Extinction event Extinction_sentence_134

There have been at least five mass extinctions in the history of life on earth, and four in the last 350 million years in which many species have disappeared in a relatively short period of geological time. Extinction_sentence_135

A massive eruptive event, that released large quantities of tephra particles into the atmosphere, is considered to be one likely cause of the "Permian–Triassic extinction event" about 250 million years ago, which is estimated to have killed 90% of species then existing. Extinction_sentence_136

There is also evidence to suggest that this event was preceded by another mass extinction, known as Olson's Extinction. Extinction_sentence_137

The Cretaceous–Paleogene extinction event (K–Pg) occurred 66 million years ago, at the end of the Cretaceous period, and is best known for having wiped out non-avian dinosaurs, among many other species. Extinction_sentence_138

Modern extinctions Extinction_section_11

Main article: Holocene extinction Extinction_sentence_139

Further information: Deforestation and Defaunation Extinction_sentence_140

According to a 1998 survey of 400 biologists conducted by New York's American Museum of Natural History, nearly 70% believed that the Earth is currently in the early stages of a human-caused mass extinction, known as the Holocene extinction. Extinction_sentence_141

In that survey, the same proportion of respondents agreed with the prediction that up to 20% of all living populations could become extinct within 30 years (by 2028). Extinction_sentence_142

A 2014 special edition of Science declared there is widespread consensus on the issue of human-driven mass species extinctions. Extinction_sentence_143

A 2020 study published in PNAS stated that the contemporary extinction crisis "may be the most serious environmental threat to the persistence of civilization, because it is irreversible." Extinction_sentence_144

Biologist E. Extinction_sentence_145 O. Wilson estimated in 2002 that if current rates of human destruction of the biosphere continue, one-half of all plant and animal species of life on earth will be extinct in 100 years. Extinction_sentence_146

More significantly, the current rate of global species extinctions is estimated as 100 to 1,000 times "background" rates (the average extinction rates in the evolutionary time scale of planet Earth), while future rates are likely 10,000 times higher. Extinction_sentence_147

However, some groups are going extinct much faster. Extinction_sentence_148

Biologists Paul R. Ehrlich and Stuart Pimm, among others, contend that human population growth and overconsumption are the main drivers of the modern extinction crisis. Extinction_sentence_149

In January 2020, the UN's Convention on Biological Diversity drafted a plan to mitigate the contemporary extinction crisis by establishing a deadline of 2030 to protect 30% of the earth's land and oceans and reduce pollution by 50%, with the goal of allowing for the restoration of ecosystems by 2050. Extinction_sentence_150

The 2020 United Nations' Global Biodiversity Outlook report stated that of the 20 biodiversity goals laid out by the Aichi Biodiversity Targets in 2010, only 6 were "partially achieved" by the deadline of 2020. Extinction_sentence_151

The report warned that biodiversity will continue to decline if the status quo is not changed, in particular the "currently unsustainable patterns of production and consumption, population growth and technological developments". Extinction_sentence_152

History of scientific understanding Extinction_section_12

For much of history, the modern understanding of extinction as the end of a species was incompatible with the prevailing worldview. Extinction_sentence_153

Prior to the 19th century, much of Western society adhered to the belief that the world was created by God and as such was complete and perfect. Extinction_sentence_154

This concept reached its heyday in the 1700s with the peak popularity of a theological concept called the great chain of being, in which all life on earth, from the tiniest microorganism to God, is linked in a continuous chain. Extinction_sentence_155

The extinction of a species was impossible under this model, as it would create gaps or missing links in the chain and destroy the natural order. Extinction_sentence_156

Thomas Jefferson was a firm supporter of the great chain of being and an opponent of extinction, famously denying the extinction of the woolly mammoth on the grounds that nature never allows a race of animals to become extinct. Extinction_sentence_157

A series of fossils were discovered in the late 17th century that appeared unlike any living species. Extinction_sentence_158

As a result, the scientific community embarked on a voyage of creative rationalization, seeking to understand what had happened to these species within a framework that did not account for total extinction. Extinction_sentence_159

In October 1686, Robert Hooke presented an impression of a nautilus to the Royal Society that was more than two feet in diameter, and morphologically distinct from any known living species. Extinction_sentence_160

Hooke theorized that this was simply because the species lived in the deep ocean and no one had discovered them yet. Extinction_sentence_161

While he contended that it was possible a species could be "lost", he thought this highly unlikely. Extinction_sentence_162

Similarly, in 1695, Sir Thomas Molyneux published an account of enormous antlers found in Ireland that did not belong to any extant taxa in that area. Extinction_sentence_163

Molyneux reasoned that they came from the North American moose and that the animal had once been common on the British Isles. Extinction_sentence_164

Rather than suggest that this indicated the possibility of species going extinct, he argued that although organisms could become locally extinct, they could never be entirely lost and would continue to exist in some unknown region of the globe. Extinction_sentence_165

The antlers were later confirmed to be from the extinct deer Megaloceros. Extinction_sentence_166

Hooke and Molyneux's line of thinking was difficult to disprove. Extinction_sentence_167

When parts of the world had not been thoroughly examined and charted, scientists could not rule out that animals found only in the fossil record were not simply "hiding" in unexplored regions of the Earth. Extinction_sentence_168

Georges Cuvier is credited with establishing the modern conception of extinction in a 1796 lecture to the French Institute, though he would spend most of his career trying to convince the wider scientific community of his theory. Extinction_sentence_169

Cuvier was a well-regarded geologist, lauded for his ability to reconstruct the anatomy of an unknown species from a few fragments of bone. Extinction_sentence_170

His primary evidence for extinction came from mammoth skulls found in the Paris basin. Extinction_sentence_171

Cuvier recognized them as distinct from any known living species of elephant, and argued that it was highly unlikely such an enormous animal would go undiscovered. Extinction_sentence_172

In 1812, Cuvier, along with Alexandre Brongniart and Geoffroy Saint-Hilaire, mapped the strata of the Paris basin. Extinction_sentence_173

They saw alternating saltwater and freshwater deposits, as well as patterns of the appearance and disappearance of fossils throughout the record. Extinction_sentence_174

From these patterns, Cuvier inferred historic cycles of catastrophic flooding, extinction, and repopulation of the earth with new species. Extinction_sentence_175

Cuvier's fossil evidence showed that very different life forms existed in the past than those that exist today, a fact that was accepted by most scientists. Extinction_sentence_176

The primary debate focused on whether this turnover caused by extinction was gradual or abrupt in nature. Extinction_sentence_177

Cuvier understood extinction to be the result of cataclysmic events that wipe out huge numbers of species, as opposed to the gradual decline of a species over time. Extinction_sentence_178

His catastrophic view of the nature of extinction garnered him many opponents in the newly emerging school of uniformitarianism. Extinction_sentence_179

Jean-Baptiste Lamarck, a gradualist and colleague of Cuvier, saw the fossils of different life forms as evidence of the mutable character of species. Extinction_sentence_180

While Lamarck did not deny the possibility of extinction, he believed that it was exceptional and rare and that most of the change in species over time was due to gradual change. Extinction_sentence_181

Unlike Cuvier, Lamarck was skeptical that catastrophic events of a scale large enough to cause total extinction were possible. Extinction_sentence_182

In his geological history of the earth titled Hydrogeologie, Lamarck instead argued that the surface of the earth was shaped by gradual erosion and deposition by water, and that species changed over time in response to the changing environment. Extinction_sentence_183

Charles Lyell, a noted geologist and founder of uniformitarianism, believed that past processes should be understood using present day processes. Extinction_sentence_184

Like Lamarck, Lyell acknowledged that extinction could occur, noting the total extinction of the dodo and the extirpation of indigenous horses to the British Isles. Extinction_sentence_185

He similarly argued against mass extinctions, believing that any extinction must be a gradual process. Extinction_sentence_186

Lyell also showed that Cuvier's original interpretation of the Parisian strata was incorrect. Extinction_sentence_187

Instead of the catastrophic floods inferred by Cuvier, Lyell demonstrated that patterns of saltwater and freshwater deposits, like those seen in the Paris basin, could be formed by a slow rise and fall of sea levels. Extinction_sentence_188

The concept of extinction was integral to Charles Darwin's On the Origin of Species, with less fit lineages disappearing over time. Extinction_sentence_189

For Darwin, extinction was a constant side effect of competition. Extinction_sentence_190

Because of the wide reach of On the Origin of Species, it was widely accepted that extinction occurred gradually and evenly (a concept now referred to as background extinction). Extinction_sentence_191

It was not until 1982, when David Raup and Jack Sepkoski published their seminal paper on mass extinctions, that Cuvier was vindicated and catastrophic extinction was accepted as an important mechanism. Extinction_sentence_192

The current understanding of extinction is a synthesis of the cataclysmic extinction events proposed by Cuvier, and the background extinction events proposed by Lyell and Darwin. Extinction_sentence_193

Human attitudes and interests Extinction_section_13

Extinction is an important research topic in the field of zoology, and biology in general, and has also become an area of concern outside the scientific community. Extinction_sentence_194

A number of organizations, such as the Worldwide Fund for Nature, have been created with the goal of preserving species from extinction. Extinction_sentence_195

Governments have attempted, through enacting laws, to avoid habitat destruction, agricultural over-harvesting, and pollution. Extinction_sentence_196

While many human-caused extinctions have been accidental, humans have also engaged in the deliberate destruction of some species, such as dangerous viruses, and the total destruction of other problematic species has been suggested. Extinction_sentence_197

Other species were deliberately driven to extinction, or nearly so, due to poaching or because they were "undesirable", or to push for other human agendas. Extinction_sentence_198

One example was the near extinction of the American bison, which was nearly wiped out by mass hunts sanctioned by the United States government, to force the removal of Native Americans, many of whom relied on the bison for food. Extinction_sentence_199

Biologist Bruce Walsh states three reasons for scientific interest in the preservation of species: genetic resources, ecosystem stability, and ethics; and today the scientific community "stress[es] the importance" of maintaining biodiversity. Extinction_sentence_200

In modern times, commercial and industrial interests often have to contend with the effects of production on plant and animal life. Extinction_sentence_201

However, some technologies with minimal, or no, proven harmful effects on Homo sapiens can be devastating to wildlife (for example, DDT). Extinction_sentence_202

Biogeographer Jared Diamond notes that while big business may label environmental concerns as "exaggerated", and often cause "devastating damage", some corporations find it in their interest to adopt good conservation practices, and even engage in preservation efforts that surpass those taken by national parks. Extinction_sentence_203

Governments sometimes see the loss of native species as a loss to ecotourism, and can enact laws with severe punishment against the trade in native species in an effort to prevent extinction in the wild. Extinction_sentence_204

Nature preserves are created by governments as a means to provide continuing habitats to species crowded by human expansion. Extinction_sentence_205

The 1992 Convention on Biological Diversity has resulted in international Biodiversity Action Plan programmes, which attempt to provide comprehensive guidelines for government biodiversity conservation. Extinction_sentence_206

Advocacy groups, such as The Wildlands Project and the Alliance for Zero Extinctions, work to educate the public and pressure governments into action. Extinction_sentence_207

People who live close to nature can be dependent on the survival of all the species in their environment, leaving them highly exposed to extinction risks. Extinction_sentence_208

However, people prioritize day-to-day survival over species conservation; with human overpopulation in tropical developing countries, there has been enormous pressure on forests due to subsistence agriculture, including slash-and-burn agricultural techniques that can reduce endangered species's habitats. Extinction_sentence_209

Antinatalist philosopher David Benatar concludes that any popular concern about non-human species extinction usually arises out of concern about how the loss of a species will impact human wants and needs, that "we shall live in a world impoverished by the loss of one aspect of faunal diversity, that we shall no longer be able to behold or use that species of animal." Extinction_sentence_210

He notes that typical concerns about possible human extinction, such as the loss of individual members, are not considered in regards to non-human species extinction. Extinction_sentence_211

Planned extinction Extinction_section_14

Main article: Eradication of infectious diseases Extinction_sentence_212

Completed Extinction_section_15

Extinction_unordered_list_0

  • The smallpox virus is now extinct in the wild, although samples are retained in laboratory settings.Extinction_item_0_0
  • The rinderpest virus, which infected domestic cattle, is now extinct in the wild.Extinction_item_0_1

Proposed Extinction_section_16

The poliovirus is now confined to small parts of the world due to extermination efforts. Extinction_sentence_213

Dracunculus medinensis, a parasitic worm which causes the disease dracunculiasis, is now close to eradication thanks to efforts led by the Carter Center. Extinction_sentence_214

Treponema pallidum pertenue, a bacterium which causes the disease yaws, is in the process of being eradicated. Extinction_sentence_215

Biologist Olivia Judson has advocated the deliberate extinction of certain disease-carrying mosquito species. Extinction_sentence_216

In a September 25, 2003 article in The New York Times, she advocated "specicide" of thirty mosquito species by introducing a genetic element which can insert itself into another crucial gene, to create recessive "knockout genes". Extinction_sentence_217

She says that the Anopheles mosquitoes (which spread malaria) and Aedes mosquitoes (which spread dengue fever, yellow fever, elephantiasis, and other diseases) represent only 30 of around 3,500 mosquito species; eradicating these would save at least one million human lives per annum, at a cost of reducing the genetic diversity of the family Culicidae by only 1%. Extinction_sentence_218

She further argues that since species become extinct "all the time" the disappearance of a few more will not destroy the ecosystem: "We're not left with a wasteland every time a species vanishes. Extinction_sentence_219

Removing one species sometimes causes shifts in the populations of other species—but different need not mean worse." Extinction_sentence_220

In addition, anti-malarial and mosquito control programs offer little realistic hope to the 300 million people in developing nations who will be infected with acute illnesses this year. Extinction_sentence_221

Although trials are ongoing, she writes that if they fail: "We should consider the ultimate swatting." Extinction_sentence_222

Biologist E. Extinction_sentence_223 O. Wilson has advocated the eradication of several species of mosquito, including malaria vector Anopheles gambiae. Extinction_sentence_224

Wilson stated, "I'm talking about a very small number of species that have co-evolved with us and are preying on humans, so it would certainly be acceptable to remove them. Extinction_sentence_225

I believe it's just common sense." Extinction_sentence_226

Cloning Extinction_section_17

Main article: De-extinction Extinction_sentence_227

Some, such as Harvard geneticist George M. Church, believe that ongoing technological advances will let us "bring back to life" an extinct species by cloning, using DNA from the remains of that species. Extinction_sentence_228

Proposed targets for cloning include the mammoth, the thylacine, and the Pyrenean ibex. Extinction_sentence_229

For this to succeed, enough individuals would have to be cloned, from the DNA of different individuals (in the case of sexually reproducing organisms) to create a viable population. Extinction_sentence_230

Though bioethical and philosophical objections have been raised, the cloning of extinct creatures seems theoretically possible. Extinction_sentence_231

In 2003, scientists tried to clone the extinct Pyrenean ibex (C. p. pyrenaica). Extinction_sentence_232

This attempt failed: of the 285 embryos reconstructed, 54 were transferred to 12 mountain goats and mountain goat-domestic goat hybrids, but only two survived the initial two months of gestation before they too died. Extinction_sentence_233

In 2009, a second attempt was made to clone the Pyrenean ibex: one clone was born alive, but died seven minutes later, due to physical defects in the lungs. Extinction_sentence_234

See also Extinction_section_18

Credits to the contents of this page go to the authors of the corresponding Wikipedia page: en.wikipedia.org/wiki/Extinction.