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Extinction Continuum

A continuum of genetic predicaments is represented in this diagram, matched with a continuum of genetic rescue techniques. Technologies on the left can readily be used in conservation of living species. Emerging methods on the right make reviving extinct species possible. When combined these technologies create pathways for genetic assistance and de-extinction.

Stages of Species Endangerment

Endangered
Critically Endangered
Extinct
<p>The 80,000 living giraffes were classified into 8 subspecies by differences in coat color, but are now considered separate species, some of which are very rare. The Nigerian Giraffe numbers less than 200 individuals and the Rothschild’s Giraffe only 1,100.</p>
<span class='wiki-link'><a href='' target='_blank'></a></span> <p>The Houbara is a large desert bird of the Middle East. It is currently listed as vulnerable by IUCN. Its population is decreasing due to unregulated trapping for use in the falconer industry.</p>
<span class='wiki-link'><a href='' target='_blank'></a></span> <p>While not endangered, the African wild cat is a model species for the use of advanced reproductive technology in rare cats. Experiments have been successful with in vitro fertilization, embryonic transfer, and cloning.</p>
<span class='wiki-link'><a href='' target='_blank'></a></span> <p>The black-footed ferret was thought to be extinct, but a remnant population was discovered in 1981. All the living black-footed ferrets (about 1,300) are descended from 7 individuals of this population.</p>
<span class='wiki-link'><a href='' target='_blank'></a></span> <p>In the past 30 years, chytrid fungus has caused the decline and extinction of almost 200 species of frogs. New research is revealing that some types of bacteria could provide anti-fungal treatment for the disease.</p>
<span class='wiki-link'><a href='' target='_blank'></a></span> <p>This is the last wild horse species in the world. It nearly became extinct. Captive breeding from 14 individuals has brought the population to over 1,800 horses, with more than 300 now sustaining in the wild: a conservation success.</p>
<span class='wiki-link'><a href='' target='_blank'></a></span> <p>American bat populations have decreased 80% in the past five years due to White Nose Syndrome, a fungal disease. Bioengineering may provide a method for saving bats from this fungal disease.</p>
<span class='wiki-link'><a href='' target='_blank'></a></span> <p>Of the 50 or so honeycreeper species, nearly 20 have gone extinct due to human activities. Invasive avian malaria threatens many species with extinction. Genomic technologies could provide ways to give these species immunity.</p>
<span class='wiki-link'><a href='' target='_blank'></a></span> <p>The Northern white rhinoceros is a distinct species of rhinoceros. Only 4 living individuals remain, but cryopreserved cells of 7 more individuals could be used to repopulate this species using cross-species cloning.</p>
<span class='wiki-link'><a href='' target='_blank'></a></span> <p>Little is known about this subspecies of wallaby, but fewer than 200 are alive and it is now extinct in the wild of the Australian outback.</p>
<span class='wiki-link'><a href='' target='_blank'></a></span> <p>Frozen cells from a single female were cryogenically preserved before this species went extinct in the year 2000. Using living goats as surrogate mothers it is hoped that cloning will revive this species.</p>
<span class='wiki-link'><a href='' target='_blank'></a></span> <p>The Dodo went extinct in the late 1600’s, and only one tissue specimen has survived to the present. DNA from this specimen confirmed that the Dodo bird is a species of giant pigeon.</p>
<span class='wiki-link'><a href='' target='_blank'></a></span> <p>The passenger pigeon was once the most abundant bird in North America, but in less than 50 years was driven to extinction due to commercial food markets.</p>
<span class='wiki-link'><a href='' target='_blank'></a></span> <p>The mammoth went extinct in the past 10,000 years, but left behind many remains with retrievable DNA. This species has been key in establishing much of the genomic research used for extinct species.</p>
<span class='wiki-link'><a href='' target='_blank'></a></span> <p>DNA sequencing from ground sloth feces have shown that at least one type of ground sloth liked eating mustard seeds. While we can sequence the genome of the ground sloth, no living sloth could bear the extinct species’ offspring.</p>
<span class='wiki-link'><a href='' target='_blank'></a></span> <p>The Macrauchenia is an ungulate from prehistoric South America. Fossils could produce DNA, but no living relative exists to assemble the genetic code and proceed with de-extinction.</p>
<span class='wiki-link'><a href='' target='_blank'></a></span> <p>The oldest DNA sequence to date is 700,000 years old. Under the best conditions, DNA may only survive up to 1.5 million years. All non-avian dinosaurs went extinct 65 million years ago. No DNA means that de-extinction is not possible.</p>
<span class='wiki-link'><a href='' target='_blank'></a></span>
Declining Severe Bottleneck Extinct in the Wild
Degrading DNA
No DNA
Recovering
Reintroduction
Revivable

How Biotechnology Can Help


Remnant populations of endangered species often become so small and inbred that they suffer from decreasing variability in their gene pool. Their situation can be analyzed with Comparative Genomics (becoming a common practice in conservation biology). Cloning can be used for gene pool enrichment.

The “ancient DNA” of many extinct species can be recovered from museum specimens and fossils via Ancient Genome Assembly. New techniques still being further developed (Synthetic DNA and CRISPR Genome Editing) may be able to bring the reassembled genomes back to life via a close living relative. But species that died out so long ago that no DNA remains, such as dinosaurs, are unrecoverably extinct.