- Also called:
- resurrection biology
- Related Topics:
- evolution
- genetic engineering
- biotechnology
- extinction
de-extinction
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What is de-extinction?
De-extinction is the process of reviving species that have died out using methods like selective breeding, genetics, and cloning.
Back breeding relies on selectively breeding species with traits similar to extinct ancestors. Modern genetic technologies allow scientists to isolate DNA from the remains of extinct animals. Scientists can then reconstruct genetic sequences of extinct species and compare them to extant species.
Somatic cell nuclear transfer (SCNT) is another tool used for de-extinction, which involves transferring the nucleus of a somatic cell into an enucleated egg to create an embryo. The embryo is then transplanted into a surrogate mother.
De-extinction can help advance knowledge in genetics and developmental biology and has also raised ethical questions about altering natural history, the welfare of resurrected species, and conservation efforts.
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Why do scientists want to bring extinct species back to life?
Scientists are interested in de-extinction, or resurrecting extinct species, because it offers an opportunity to correct past harms to other species and increase species diversity. Advances in selective breeding, genetics, and reproductive cloning technologies have made this once-fanciful idea a possibility. De-extinction can advance science, especially in developmental biology and genetics, and raise interest in endangered species, as de-extinction tools can also be applied to endangered species conservation, such as restoring genetic diversity.
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What methods can be used to try de-extinction?
De-extinction methods include back breeding, cloning, stem cell manipulation, genome reconstruction, and genome editing.
- Back breeding uses selective breeding to produce breeds with traits of wild ancestors.
- Cloning via somatic cell nuclear transfer (SCNT) involves transplanting a somatic cell nucleus into an enucleated egg, stimulating cell division, and implanting the embryo into a surrogate mother.
- Stem cells can be manipulated to differentiate into sperm and eggs.
- Genome editing adds or removes specific DNA pieces in a species’s genome, facilitated by CRISPR technology.
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What are some examples of animals scientists are trying to revive?
De-extinction is the process of reviving species that have died out, using methods like cloning, selective breeding, and genetic engineering.
Examples of species that scientists are considering for de-extinction include:
* Woolly mammoth: died out due to climate change and hunting by humans.
* Passenger pigeon: became extinct in the early 20th century due to hunting and habitat loss.
* Thylacine: also known as the Tasmanian tiger, disappeared in the 20th century due to hunting and habitat destruction.
* Pyrenean ibex: also known as the bucardo. In 2009, scientists were almost successful in bringing it back from extinction, but the clone died shortly after birth.
* Gastric-brooding frog: extinct species of Australian frog.3 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
What challenges or problems might happen if we bring extinct animals back?
Bringing back extinct animals through de-extinction raises several potential challenges:
- Ethical Concerns De-extinction could unintentionally condone extinction by suggesting species can always be brought back.
- Ecological Impact Many extinct species disappeared due to habitat loss, and resurrected species might struggle to adapt to current environmental conditions. Reintroduced species could also face high failure rates, as seen in previous introduction attempts.
- Genetic Diversity Small populations of resurrected species may lack genetic variation, reducing their ability to adapt to changing environments and increasing their risk of extinction.
- Classification Uncertainties It is unclear how to classify species revived through back breeding, cloning, or genetic reconstruction, especially if they diverge genetically from the original extinct species.
- Resource Constraints Resurrected species would likely be endangered and require conservation efforts, potentially straining already limited resources.
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How could de-extinction affect the environment and living species today?
De-extinction, the revival of extinct species, could have both positive and negative effects on the environment and extant species. It offers an opportunity to restore lost biodiversity and rectify past human-caused harms, but resurrected species may struggle to adapt to current environmental conditions, especially if their former habitats have been altered or destroyed.
Moreover, the allocation of resources for de-extinction could divert attention and funding from endangered species conservation. Ethical concerns exist regarding the well-being and classification of resurrected animals, as well as the potential for unintended consequences that threaten biodiversity. While de-extinction can advance knowledge in genetics and developmental biology, its impact necessitates careful consideration.
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de-extinction, the process of resurrecting species that have died out, or gone extinct. Although once considered a fanciful notion, the possibility of bringing extinct species back to life has been raised by advances in selective breeding, genetics, and reproductive cloning technologies. Key among those advances was the development in the 1990s of a technique known as somatic cell nuclear transfer (SCNT), which was used to produce the first mammalian clone, Dolly the sheep (born 1996, died 2003).
In 2009, using SCNT, scientists very nearly achieved de-extinction for the first time, attempting to bring back the extinct Pyrenean ibex (or bucardo, Capra pyrenaica pyrenaica). A clone was produced from preserved tissues, but it died from a severe lung defect within minutes of being born. The near success of the attempt sparked debate about whether species should be brought back from extinction and, if they are brought back, how it should be done and how the species should be managed.
The candidate species for de-extinction are many. Some high-profile examples include the woolly mammoth (Mammuthus primigenius), the passenger pigeon (Ectopistes migratorius), the thylacine (Thylacinus cynocephalus), and the gastric-brooding frog (Rheobatrachus silus). De-extinction does not extend to dinosaurs, partly because of the extreme old age of specimens and the severe degradation of DNA over time.
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The tools of species resurrection
The possibility of bringing extinct species back to life was first explored in the early 20th century, through an approach known as back breeding (or breeding back). Back breeding, for the production of a breed that displays the traits of a wild ancestor, is based on the principles of selective breeding, which humans have used for centuries to develop animals with desired traits. In the 1920s and ’30s, German zoologists Lutz and Heinz Heck crossbred different types of cattle in an attempt to back breed for an animal that resembled the aurochs (Bos primigenius), an extinct species of European wild ox ancestral to modern cattle. The Heck brothers crossbred modern cattle based on historical descriptions and bone specimens that provided morphological information about the aurochs but had no insight into the animals’ genetic relatedness. As a consequence, the resulting Heck cattle bore little resemblance to the aurochs.
In the latter part of the 20th century, tools emerged that enabled scientists to isolate and analyze DNA from the bones, hair, and other tissues of dead animals. Coupled with advances in reproductive technologies such as in vitro fertilization, researchers were able to identify cattle that are close genetic relatives of the aurochs and combine their sperm and eggs to produce an animal (the so-called tauros) that is morphologically and genetically similar to the aurochs.
Other advances in genetic technologies have raised the possibility of inferring and reconstructing the genetic sequences of extinct species from even poorly preserved or cryopreserved specimens. Reconstructed sequences could be compared against the sequences of extant species, allowing for the identification of not only living species or breeds best suited for back breeding but also genes that would be candidates for editing in living species. Genome editing, a technique of synthetic biology, involves adding or removing specific pieces of DNA in a species’s genome. The discovery of CRISPR (clustered regularly interspaced short palindromic repeats), a naturally occurring enzyme system that edits DNA in certain microorganisms, greatly facilitated the refinement of genome editing for de-extinction.
Cloning for de-extinction has centred primarily on the use of SCNT. SCNT entails the transfer of the nucleus from a somatic (body) cell of the animal to be cloned into the cytoplasm of an enucleated donor egg (an egg cell that came from another animal and that has had its own nucleus removed). The egg cell is stimulated in the laboratory to initiate cell division, leading to the formation of an embryo. The embryo is then transplanted into the uterus of a surrogate mother, which in the case of de-extinction is a species closely related to the one that is being cloned. In the attempt to resurrect the extinct Pyrenean ibex in 2009, researchers transferred nuclei from thawed fibroblasts of cryopreserved skin specimens into enucleated eggs of domestic goats. The reconstructed embryos were transplanted into either Spanish ibex or hybrid (Spanish ibex × domestic goat) females.
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It may also be possible to use stem cells to resurrect extinct species. Somatic cells can be reprogrammed through the introduction of specific genes, creating so-called induced pluripotent stem (iPS) cells. Such cells can be stimulated to differentiate into different cell types, including sperm and eggs that potentially can give rise to living organisms. Similar to the other techniques of de-extinction, however, the success of an approach based on stem cells depends largely on the quality of DNA that is available in preserved specimens.