Revitalization of extinct animal species

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The “revival” of extinct animal species (also called “ de-extinction ” or “ resurrection biology ”) refers to the process of reviving extinct or endangered animal species, especially using genetic methods. Although until today (as of December 2018) - despite individual almost successful attempts (e.g. Lazarus project ) - no successful application has existed, numerous scientists continue to believe that resuscitation using currently known techniques is still possible in principle. A scientific debate is developing about possible applications, their consequences and related ethical problems with increasing external impact.

Methods

Three methods are discussed for the revival of extinct species:

  • Cloning , the creation of a genetically identical individual from tissue samples, is the most discussed method. The nucleus of a preserved cell has to be filled into an enucleated egg cell and this has to be implanted in a mother animal for delivery. It might also be possible to completely synthesize the genome of a species that has been gradually sequenced from various fragments and use it as a basis.
  • A closely related species of the extinct animal could be used to insert more and more DNA sequences of the extinct animal into its germline over generations with the help of genetic engineering . In this way one could generate individuals that gradually become more and more similar to the extinct species. The entire genome may not be required for this, as sections are similar. The research group of George M. Church at Harvard is working on such methods. Techniques such as multiplex automated genome engineering (MAGE) can use tailor-made oligonucleotides to insert precisely modified sequences, even if longer sequences still cause problems.
  • A third possibility is real back- breeding , provided that the genetic makeup of the extinct species is largely present in still living offspring. This is especially the case with extinct wild species, of which living descendants exist as pets , such as the aurochs . Strategic breeding can piecewise recreate the anatomy and phenotype of the extinct animal. A practical experiment with aurochs has been running since 2008 with the Tauros program .

Resuscitation projects planned

The dodo is waiting to be resurrected.

Resuscitation is attempted or intensely discussed in various animal species, often because the animals were very popular or exceptionally well-preserved specimens or close relatives are available.

  • The pigeon ( Ectopistes migratorius ), which was able to form schools with several billion animals, was extremely common in the 19th century and was hunted so excessively that the species became extinct. Stuffed specimens, which are still in stock in many museums, still contain well-preserved genetic material . This should be compared with that of the closely related, still living scaled- neck pigeon and deviations should be modified with the help of genetic methods so that a migrating pigeon embryo can arise. However, so that the animals can live out their social behavior, many thousands have to be reared at the same time, as the animals show neurotic behavior when the swarm is too small.
  • The last specimens of the woolly mammoth ( Mammuthus primigenius ) became extinct 3700 years ago on the Siberian Wrangel Island. In 2007, the largely intact genome of the woolly mammoth was extracted from frozen remains.
  • Aurochs ( Bos primigenius ), whose shoulder height could be up to 1.80 meters, died out in Europe about 400 years ago. As part of the Tauros program , aurochs ( Bos primigenius ) are to be recreated through back-breeding with the participation of various universities and foundations .
  • The dodo ( Raphus cucullatus ) is a prominent extinct, flightless bird that lived on the island of Mauritius in the Indian Ocean. However, being both tasty and trusting, it was eaten by sailors and exterminated in 1662. There are still some stuffed specimens of the animals in museums today, at least one of which is said to contain soft tissues. In addition, fossil and mummified remains also exist on the island of Mauritius. Since the dodo is closely related to the pigeon, it could serve both as a “comparison blueprint” and also raise the dodo young.
  • The Pyrenean Ibex ( Capra pyrenaica pyrenaica ) is an extinct subspecies of the Iberian Ibex. This died out in 2000, but a Pyrenean ibex fawn was cloned using the cell sample in 2009. It was the first animal to be cloned from an extinct subspecies. However, the young ibex died after a few minutes, with which the subspecies died out again.
  • The quagga ( Equus quagga quagga ) is an extinct zebra shape. It is considered a southern subspecies of the plains zebra ( Equus quagga ). The quagga was exterminated by humans at the end of the 19th century . Several genetic studies confirmed the close relationship with the plains zebra, the DNA analyzes published in 1984 also prompted the start of an image breeding project of the quaggas from southern plains zebras. Especially individual representatives of the southern subspecies of the plains zebra ( Eq burchelli ) show a clear reduction in stripes, which is reminiscent of the quagga. In the meantime, the Quagga Project , initiated by taxidermist Reinhold Rau (1932-2006) in 1986, tries to build up a plains zebra breeding line through selective breeding, which externally resembles the Quaggas. Several copies from the third generation already show a considerable reduction in stripes. The aim of the project is to create an animal that looks very similar to the quagga and can possibly be released into the wild in the former habitats.

Resuscitation by cloning

The half-life of DNA under realistic, reasonably favorable conditions is a few hundred years. Scientists therefore rule out the cloning of DNA if the age of the DNA exceeds this period. It does not seem to be ruled out that short sequence fragments in fossil material e.g. B. to find from the Mesozoic era . The existence of longer sequences or even an entire genome is excluded to this extent. All information published so far about such old sequences has proven to be artifacts caused by contamination.

Pyrenean Ibex clone attempt

A subspecies of the Iberian ibex , the Pyrenean ibex ( Capra pyrenaica pyrenaica ) was cloned in 2009 with the help of domestic goat foster mothers after the last known specimen died in an accident in 2000 in the Pyrenees Ordesa National Park . 439 embryos were created from frozen tissue samples from the last animal; 57 of them could be implanted in goats, but only seven successfully implanted in the uterine lining . Eventually a clone was born, but it died surprisingly quickly within minutes of a pulmonary embolism . This means that the species has become extinct a second time.

Cloning experiment of the southern gastric breeder frog ("Lazarus project")

In March 2013, the University of New South Wales succeeded in growing living embryos of the southern gastric breeder frog ( Rheobatrachus silus ), a species from the genus of gastric breeder frogs , by implanting thawed ("dead") genomes from cryopreservation in egg cells of a distantly related frog species . Although the resulting embryos did not survive the early stage, their cells are to be used in the further course of the “ Lazarus Project ” to “revive” an extinct animal species for the first time by means of cloning .

Revival through back-breeding

Alison Woollard, an Oxford University biochemist , believes it is possible to recreate dinosaurs from birds through purposeful, breeding- induced retrogressive succession .

Hans Larsson, a scientist at McGill University in Montreal, is working on re-activating dinosaur properties that disappeared in birds millions of years ago. The corresponding genes for the development of tails, claws and teeth are still present, but methylated and thus switched off. Larsson hypothesizes that the dinosaur anatomy can be reproduced by activating certain genetic levers during the development of a chicken embryo.

Philosophical examination of the concept

The revival of extinct animal species is controversial. There are both critics and supporters of the idea.

Advocates

The genetics professor George Church from Harvard University advocates the revival of extinct animal species with the argument that certain critical "key species" should be saved from extinction with the help of genetic engineering or simply "revived" because their absence would otherwise have catastrophic consequences for that ecosystem dominated by them. For example, mammoths would have to be cloned or elephants converted into “functional mammoths”, since only their influence on the tundra can prevent the greenhouse effect from escalating through rising methane gas.

According to the Swedish environmental historian Dolly Jørgensen, the problems would be comparable to those encountered with the release of locally extinct species in earlier habitats; these are generally considered to be manageable.

criticism

Numerous experts are skeptical or even negative about the revival of extinct animal species using genetic engineering methods; essential arguments are for example:

  • To attempt would be hubris to reject the result as unnatural.
  • There would always be very few animal species to be revived, so that the finality of the extinction of the other species would be masked.
  • The method would certainly only benefit a few charismatic, famous species.
  • The high costs draw money away from the more promising saving of still living species and could possibly be in direct competition with their conservation.
  • The habitats of the extinct species would be greatly changed so that they would no longer find a place.
  • Species could potentially become harmful, or potentially dangerous pathogens such as viruses could be reborn.
  • In addition, the imperfections of cloning pose a great risk of producing animals with reduced viability which would then be subjected to unnecessary suffering.

The revival of extinct hominids such as the Neanderthal man would cause particular ethical problems. However, this is also being seriously discussed.

Fiction - The Resurrection of Dinosaurs

The dinosaurs surpass all other fossil animal groups in popularity, as both their sometimes huge appearance and the fact that they did not live at the same time as humans exert a special fascination. Hence, dinosaur resuscitation is of great interest. In the movie Jurassic Park , based on the novel of the same name by Michael Crichton , various dinosaurs are brought back to life using genetic information from dinosaur blood , which comes from blood-sucking insects that have survived enclosed in amber . The novel and especially its cinematic implementation enjoy great popularity worldwide, and the concept - today scientifically refuted - has often been discussed with varying degrees of seriousness. The mechanism shown in the film fails because insects fossilized in amber (such as mosquitoes) are not preserved as body fossils, but only as an empty shell encasing a cavity.

See also

literature

Web links

Individual evidence

  1. ↑ Jacob S. Sherkow and Henry T. Greely (2013): What If Extinction Is Not Forever? Science Vol 340: 32-33. doi : 10.1126 / science.1236965
  2. ↑ a b c d "How to Resurrect Lost Species"
  3. ↑ Harris H Wang, Hwangbeom Kim, Le Cong, Jaehwan Jeong, Duhee Bang, George M. Church (2009): Genome-scale engineering promoter by coselection MAGE. Nature Methods Vol.9, No.6: 591. doi : 10.1038 / nmeth.1971
  4. ↑ a b website of the project
  5. ↑ Blockstein (2002), section Demography and Populations / Population Status , see literature
  6. ↑ "brought to life"
  7. ↑ Blockstein (2002), section “Conservation”, see literature
  8. ↑ "The Resurrection of Mammoths and Aurochs"
  9. ^ "Pictures: Extinct Species That Could Be Brought Back - The Dodo"
  10. ↑ J. Folch, MJ Cocero, P. Chesné, JL Alabart, V. Domínguez, Y. Cognié, A. Roche, A. Fernández-Árias, JI Martí, P. Sánchez, E. Echegoyen, JF Beckers, A. Sánchez Bonastre, X. Vignon (2009): First birth of an animal from an extinct subspecies ( Capra pyrenaica pyrenaica ) by cloning , Theriogenology, Volume 71, Issue 6, Pages 1026-1034
  11. ↑ Ludovic Orlando, Jessica L. Metcalf, Maria T. Alberdi, Miguel Telles-Antunes, Dominique Bonjean, Marcel Otte , Fabiana Martin, Véra Eisenmann, Marjan Mashkour, Flavia Morello, Jose L. Prado, Rodolfo Salas-Gismondi, Bruce J. Shockey, Patrick J. Wrinn, Sergei K. Vasil'ev, Nikolai D. Ovodov, Michael I. Cherry Blair Hopwood, Dean Male, Jeremy J. Austin, Catherine Hänni, and Alan Cooper: Revising the recent evolutionary history of equids using ancient DNA . PNAS 106, 2009, pp. 21754-21759
  12. ↑ http://www.quaggaproject.org/
  13. ↑ Eric H. Harley, Michael H. Knight, Craig Lardner, Bernard Wooding, and Michael Gregor: The Quagga Project: Progress Over 20 Years of Selective Breeding . South African Journal of Wildlife Research 39 (2), 2009, pp. 155-163
  14. ↑ Morten E. Allentoft, Matthew Collins, David Harker, James Haile, Charlotte L. Oskam, Marie L. Hale, Paula F. Campos, Jose A. Samaniego, M. Thomas P. Gilbert, Eske Willerslev, Guojie Zhang, R. Paul Scofield, Richard N. Holdaway, Michael Bunce (2012): The half-life of DNA in bone: measuring decay kinetics in 158 dated fossils. Proceedings of the Royal Society London Series B 279: 4724-4733. doi : 10.1098 / rspb.2012.1745
  15. ↑ "Jurassic Park has nothing to do with reality"
  16. ↑ "First extinct animal cloned"
  17. ↑ UNSW Newsroom: Scientists produce cloned embryos of extinct frog , March 15, 2013.
  18. ↑ a b "The New Idea to Revive the Dinosaurs"
  19. ↑ "Chickenosaurus: Canadian scientist says he can create dinosaurs from chickens"
  20. ↑ "Scientists are Attempting to recreate dinosaurs by manipulating chicken DNA" ( Memento of 26 October 2014 Internet Archive )
  21. ^ Bringing Them Back to Life. The revival of an extinct species is no longer a fantasy. But is it a good idea? National Geographic, published: April 2013
  22. ↑ "Cloning: Please Revive"
  23. ↑ Dolly Jørgensen (2013): Reintroduction and De-extinction. BioScience Vol. 63 No.9: 719-720. doi : 10.1093 / bioscience / 63.9.719
  24. ↑ Sariah Cottrell, Jamie L Jensen, Steven L Peck: Resuscitation and resurrection: The ethics of cloning cheetahs, mammoths, and Neanderthals. Life Sciences, Society and Policy 10 (3). 2014, free download
  25. ↑ Zach Zorich (2010): Should We Clone Neanderthals? Archeology Volume 63 Number 2 online