In biology and ecology, extinction is the termination of an organism
or of a group of organisms (taxon), normally a species. 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. Because a species' potential
range may be very large, determining this moment is difficult, and is
usually done retrospectively. 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.
More than 99 percent of all species, amounting to over five billion
species, that ever lived on Earth are estimated to be
extinct. Estimates on the number of Earth's current species
range from 10 million to 14 million, of which about 1.2 million
have been documented and over 86 percent have not yet been
described. More recently, in May 2016, scientists reported that 1
trillion species are estimated to be on Earth currently with only
one-thousandth of one percent described.
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. The relationship between
animals and their ecological niches has been firmly established. A
typical species becomes extinct within 10 million years of its first
appearance, although some species, called living fossils, survive
with virtually no morphological change for hundreds of millions of
Mass extinctions are relatively rare events; however, isolated
extinctions are quite common. Only recently have extinctions been
recorded and scientists have become alarmed at the current high rate
of extinctions. Most species that become extinct are
never scientifically documented. Some scientists estimate that up to
half of presently existing plant and animal species may become extinct
A dagger symbol (†) placed next to the name of a species or other
taxon is often done to indicate its status as extinct.
1.2 Lazarus taxa
2.1 Genetics and demographic phenomena
2.2 Genetic pollution
2.4 Predation, competition, and disease
2.6 Climate change
3 Mass extinctions
3.1 Modern extinctions
4 History of scientific understanding
5 Human attitudes and interests
5.1 Planned extinction
6 See also
8 External links
External mold of the extinct
Lepidodendron from the Upper
Carboniferous of Ohio
A species is extinct when the last existing member dies. Extinction
therefore becomes a certainty when there are no surviving individuals
that can reproduce and create a new generation. 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.
Pinpointing the extinction (or pseudoextinction) of a species requires
a clear definition of that species. 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
Extinction of a species (or replacement by a daughter
species) plays a key role in the punctuated equilibrium hypothesis of
Stephen Jay Gould
Stephen Jay Gould and Niles Eldredge.
Skeleton of various extinct dinosaurs; some other dinosaur lineages
still flourish in the form of birds
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. This phenomenon is also known as
extirpation. Local extinctions may be followed by a replacement of the
species taken from other locations; wolf reintroduction is an example
Species which are not extinct are termed extant. Those that
are extant but threatened by extinction are referred to as threatened
or endangered species.
The dodo of Mauritius, shown here in a 1626 illustration by Roelant
Savery, is an often-cited example of modern extinction
Currently an important aspect of extinction is human attempts to
preserve critically endangered species. These are reflected by the
creation of the conservation status "extinct in the wild" (EW).
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. 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. 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.
The extinction of one species' wild population can have knock-on
effects, causing further extinctions. These are also called "chains of
extinction". This is especially common with extinction of keystone
Main article: Pseudoextinction
Extinction of a parent species where daughter species or subspecies
are still extant is called pseudoextinction or phyletic extinction.
Effectively, the old taxon vanishes, transformed (anagenesis) into a
successor, or split into more than one (cladogenesis).
Pseudoextinction is difficult to demonstrate unless one has a strong
chain of evidence linking a living species to members of a
pre-existing species. 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
Pseudoextinction is much easier to demonstrate for larger
Main article: Lazarus taxa
The coelacanth, a fish related to lungfish and tetrapods, was
considered to have been extinct since the end of the
until 1938 when a specimen was found, off the
Chalumna River (now
Tyolomnqa) on the east coast of South Africa. Museum curator
Marjorie Courtenay-Latimer discovered the fish among the catch of a
local angler, Captain Hendrick Goosen, on December 23, 1938. A
local chemistry professor, JLB Smith, confirmed the fish's importance
with a famous cable: "MOST IMPORTANT PRESERVE SKELETON AND GILLS =
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
Zoo in Tasmania in 1936; the Japanese wolf (Canis lupus
hodophilax), last sighted over 100 years ago; the ivory-billed
woodpecker (Campephilus principalis), last sighted for certain in
1944; and the slender-billed curlew (Numenius tenuirostris), not seen
The passenger pigeon, one of hundreds of species of extinct birds, was
hunted to extinction over the course of a few decades
As long as species have been evolving, species have been going
extinct. It is estimated that over 99.9% of all species that ever
lived are extinct. The average lifespan of a species is 1–10 million
years, although this varies widely between taxa. There are a
variety of causes that can contribute directly or indirectly to the
extinction of a species or group of species. "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". 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 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.
occur a long time after the events that set it in motion, a phenomenon
known as extinction debt.
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. 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. By contrast, conservation biology uses
the extinction vortex model to classify extinctions by cause. 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.
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. 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. Explosive, unsustainable human
population growth is an essential cause of the extinction crisis.
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. Several species
have also been listed as extinct since 2004.
Genetics and demographic phenomena
Extinction vortex, Genetic erosion, and Mutational meltdown
If adaptation increasing population fitness is slower than
environmental degradation plus the accumulation of slightly
deleterious mutations, then a population will go extinct. Smaller
populations have fewer beneficial mutations entering the population
each generation, slowing adaptation. 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.
Limited geographic range is the most important determinant of genus
extinction at background rates but becomes increasingly irrelevant as
mass extinction arises. Limited geographic range is a cause both
of small population size and of greater vulnerability to local
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. A
diverse or deep gene pool gives a population a higher chance in the
short term of surviving an adverse change in conditions. Effects that
cause or reward a loss in genetic diversity can increase the chances
of extinction of a species.
Population bottlenecks can dramatically
reduce genetic diversity by severely limiting the number of
reproducing individuals and make inbreeding more frequent.
Main article: Genetic pollution
Purebred wild species evolved to a specific ecology can be threatened
with extinction 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. 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 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). Such
extinctions are not always apparent from morphological (non-genetic)
observations. Some degree of gene flow is a normal evolutionarily
process, nevertheless, hybridization (with or without introgression)
threatens rare species' existence.
The gene pool of a species or a population is the variety of genetic
information in its living members. A large gene pool (extensive
genetic diversity) is associated with robust populations that can
survive bouts of intense selection. Meanwhile, low genetic diversity
(see inbreeding and population bottlenecks) reduces the range of
adaptions possible. Replacing native with alien genes narrows
genetic diversity within the original population, thereby
increasing the chance of extinction.
Scorched land resulting from slash-and-burn agriculture
Habitat degradation is currently the main anthropogenic cause of
species extinctions. The main cause of habitat degradation worldwide
is agriculture, with urban sprawl, logging, mining and some fishing
practices close behind. 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. 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.
Habitat degradation through toxicity can kill off a species very
rapidly, by killing all living members through contamination or
sterilizing them. It can also occur over longer periods at lower
toxicity levels by affecting life span, reproductive capacity, or
Habitat degradation can also take the form of a physical destruction
of niche habitats. 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. For example, a fern
that depends on dense shade for protection from direct sunlight can no
longer survive without forest to shelter it. Another example is the
destruction of ocean floors by bottom trawling.
Diminished resources or introduction of new competitor species also
often accompany habitat degradation.
Global warming has allowed some
species to expand their range, bringing unwelcome[according to whom?]
competition to other species that previously occupied that area.
Sometimes these new competitors are predators and directly affect prey
species, while at other times they may merely outcompete vulnerable
species for limited resources. Vital resources including water and
food can also be limited during habitat degradation, leading to
The golden toad was last seen on May 15, 1989. Decline in amphibian
populations is ongoing worldwide
Predation, competition, and disease
See also: Island restoration
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. Recently in geological time, humans have
become an additional cause of extinction (many 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. 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). In most cases, the introductions are
unsuccessful, but when an invasive alien species does become
established, the consequences can be catastrophic. 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. Human
populations may themselves act as invasive predators. 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,
CE), and New Zealand (1300–1500 CE), 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.
Main article: Coextinction
Haast's eagle and moa from New Zealand
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.
Coextinction can also occur when a species
loses its pollinator, or to predators in a food chain who lose their
Species coextinction is a manifestation of the
interconnectedness of organisms in complex ecosystems ... While
coextinction may not be the most important cause of species
extinctions, it is certainly an insidious one".
especially common when a keystone species goes extinct. Models suggest
that coextinction is the most common form of biodiversity loss. There
may be a cascade of coextinction across the trophic levels. Such
effects are most severe in mutualistic and parasitic relationships. 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. The moa were several species of flightless birds that
were a food source for the Haast's eagle.
Extinction risk from global warming
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 as a result of climate change has been confirmed by fossil
studies. Particularly, the extinction of amphibians during the
Carboniferous Rainforest Collapse, 305 million years ago. 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. The ecologically rich areas that would
potentially suffer the heaviest losses include the Cape Floristic
Region, and the Caribbean Basin. 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. Climate change
has also been found to be a factor in habitat loss and
Marine extinction intensity during the Phanerozoic
Millions of years ago
The blue graph shows the apparent percentage (not the absolute number)
of marine animal genera becoming extinct during any given time
interval. It does not represent all marine species, just those that
are readily fossilized. The labels of the traditional "Big Five"
extinction events and the more recently recognised End-Capitanian
extinction event are clickable hyperlinks; see
Extinction event for
more details. (source and image info)
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. A
massive eruptive event is considered to be one likely cause of the
Triassic extinction event" about 250 million years ago,
which is estimated to have killed 90% of species then existing.
There is also evidence to suggest that this event was preceded by
another mass extinction, known as Olson's Extinction. The
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.
Main article: Holocene extinction
Deforestation and Defaunation
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. 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). A 2014 special edition of Science declared there is widespread
consensus on the issue of human-driven mass species extinctions.
E. O. Wilson
E. 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. More
significantly, the current rate of global species extinctions is
estimated as 100 to 1000 times "background" rates (the average
extinction rates in the evolutionary time scale of planet
Earth), while future rates are likely 10,000 times higher.
However, some groups are going extinct much faster. Biologists Paul R.
Ehrlich and Stuart Pimm, among others, contend that human population
growth and overconsumption are the main drivers of the modern
History of scientific understanding
Dilophosaurus, one of the many extinct dinosaur genera. The cause of
Paleogene extinction event is a subject of much
debate amongst researchers
Georges Cuvier compared fossil mammoth jaws to those of living
elephants, concluding that they were distinct from any known living
For much of history, the modern understanding of extinction as the end
of a species was incompatible with the prevailing worldview. Through
the 18th century, much of Western society adhered to the belief that
the world was created by God and as such was complete and perfect.
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. 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.
Thomas Jefferson was a firm
supporter of the
Great Chain of Being
Great Chain of Being and an opponent of
extinction, famously denying the extinction of the wooly
mammoth on the grounds that nature never allows a race of animals to
A series of fossils were discovered in the late 17th century that
appeared unlike any living species. 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. 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. Hooke theorized that this was simply because
the species lived in the deep ocean and no one had discovered them
yet. While he contended that it was possible a species could be
"lost", he thought this highly unlikely. Similarly, in 1695,
Thomas Molyneux published an account of enormous antlers found in
Ireland that did not belong to any extant taxa in that area.
Molyneux reasoned that they came from the North American moose and
that the animal had once been common on the British Isles. 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. Using the antlers as evidence
for this position, Molyneux described how moose had continued to exist
North America even as they were lost to the British Isles. The
antlers were later confirmed to be from the extinct Irish elk
Megaloceros. Hooke and Molyneux's line of thinking was difficult
to disprove. 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
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. Cuvier was a well-regarded
geologist, lauded for his ability to reconstruct the anatomy of an
unknown species from a few fragments of bone. His primary evidence
for extinction came from mammoth skulls found in the Paris basin.
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. In 1812, Cuvier, along with
Alexandre Bronigniart & Geoffroy Saint-Hilaire, mapped the strata
of the Paris basin. They saw alternating saltwater and freshwater
deposits, as well as patterns of the appearance and disappearance of
fossils throughout the record. From these patterns, Cuvier
inferred historic cycles of catastrophic flooding, extinction, and
repopulation of the earth with new species.
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. The primary debate focused whether
this turnover caused by extinction was gradual or abrupt in
nature. 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. His catastrophic
view of the nature of extinction garnered him many opponents in the
newly emerging school of uniformitarianism.
Jean-Baptist Lamarck, a gradualist and colleague of Cuvier, saw the
fossils of different life forms as evidence of the mutable character
of species. 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.
Unlike Cuvier, Lamarck was skeptical that catastrophic events of a
scale large enough to cause total extinction were possible. 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.
Charles Lyell, a noted geologist and founder of uniformitarianism,
believed that past processes should be understood using present day
processes. 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. He similarly argued
against mass extinctions, believing that any extinction must be a
gradual process. Lyell also showed that Cuvier’s original
interpretation of the Parisian strata was incorrect. 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
The concept of extinction was integral to Charles Darwin’s On the
Origin of Species, with less fit lineages disappearing over time. For
Darwin, extinction was a constant side effect of competition.
Because of the wide reach of On the Origin of Species, it was widely
accepted that extinction occurred gradually and evenly (a concept we
now refer to as background extinction). 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. 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.
Human attitudes and interests
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. A number of organizations, such as the Worldwide
Fund for Nature, have been created with the goal of preserving species
from extinction. Governments have attempted, through enacting laws, to
avoid habitat destruction, agricultural over-harvesting, and
pollution. 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. 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.
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.
Biologist Bruce Walsh of the
University of Arizona
University of Arizona 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
In modern times, commercial and industrial interests often have to
contend with the effects of production on plant and animal life.
However, some technologies with minimal, or no, proven harmful effects
Homo sapiens can be devastating to wildlife (for example, DDT).
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.
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. Nature preserves are created by governments as a means to
provide continuing habitats to species crowded by human expansion. The
Convention on Biological Diversity
Convention on Biological Diversity has resulted in international
Biodiversity Action Plan programmes, which attempt to provide
comprehensive guidelines for government biodiversity conservation.
Advocacy groups, such as The Wildlands Project and the Alliance
for Zero Extinctions, work to educate the public and pressure
governments into action.
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. 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.
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." 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.
Main article: Eradication of infectious diseases
The smallpox virus is now extinct in the wild, although samples
are retained in laboratory settings.
The rinderpest virus, which infected domestic cattle, is now extinct
in the wild.
The poliovirus is now confined to small parts of the world due to
Dracunculus medinensis, a parasitic worm which causes the disease
dracunculiasis, is now close to eradication thanks to efforts led by
the Carter Center.
Treponema pallidum pertenue, a bacterium which causes the disease
yaws, is in the process of being eradicated.
Olivia Judson has advocated the deliberate extinction of
certain disease-carrying mosquito species. In a September 25, 2003 New
York Times article, 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". 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 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%. 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. Removing one
species sometimes causes shifts in the populations of other
species—but different need not mean worse." 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. Although trials are ongoing,
she writes that if they fail: "We should consider the ultimate
E. O. Wilson
E. O. Wilson has advocated the eradication of several
species of mosquito, including malaria vector
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. I believe it's just common
Main article: De-extinction
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. Proposed targets for cloning include the mammoth, the
thylacine, and the Pyrenean ibex. 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. Though bioethical and philosophical objections
have been raised, the cloning of extinct creatures seems
In 2003, scientists tried to clone the extinct
Pyrenean ibex (C. p.
pyrenaica). 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. 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.
IUCN Red List
Lists of extinct animals
Living Planet Index
Red List Index
Refugium (population biology)
Sepilok Orang Utan Rehabilitation Centre
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ISBN 978-0199549269. It is noteworthy that human concern about
human extinction takes a different form from human concern (where
there is any) about the extinction of non-human species. Most humans
who are concerned about the extinction of non-human species are not
concerned about the individual animals whose lives are cut short in
the passage to extinction, even though that is one of the best reasons
to be concerned about extinction (at least in its killing form). The
popular concern about animal extinction is usually concern for humans
–- 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
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