Extinction forms a natural part of the cycle of life. Around 50 million species currently exist on our planet but scientific research has indicated that, since life evolved on Earth, between 1 and 4 billion species could have blossomed into being only to die out and ultimately become extinct.

Species extinction can happen for a variety of different reasons, including disease, genetic obsolescence, over predation or, as illustrated by the fate of the dinosaurs, mass extinction events such as significant meteor strikes causing cataclysmic destruction and major atmospheric disturbances.The idea of resurrecting previously extinct species has been a fascination for many scientists, and was also the inspiration for the blockbuster film, Jurassic Park, in which many species of dinosaur were brought back into existence using DNA extracted from the blood contained in fossilised mosquitoes.

As anyone who has seen the film will testify, bringing such animals back into the present day had disastrous results, but is the concept possible?

The "Long Now Foundation" operates a "Revive and Restore" programme which conducts research into how to preserve endangered species, and is also committed to investigating the possibility of de-extinction through the use of DNA samples. The organisation was founded by entrepreneur Ryan Phelan and author Stewart Brand, a pair of visionaries devoted to the concept of enhancing biodiversity through the genetic rescue of endangered and extinct species. They aim to advance the science of preventing extinctions, to restore diminished ecosystems and undo the negative impact that humans may have had on animal species throughout history.The couple are assisted by Research and Science consultant Ben Novak, for whom the de-extinction of Passenger Pigeons and other columbids has been a life-long passion.

The first dedicated project to revive a totally extinct species is entitled "The Great Passenger Pigeon Comeback", a scheme that is using the latest genomic technology in an attempt to bring back a species of pigeon that has been extinct since 1914. It’s not quite "Jurassic Park" material, but the Passenger Pigeon was deemed to be a model candidate for resurrection as its DNA has the potential to thoroughly test the process of de-extinction and advance the science sufficiently so that the techniques could be applied subsequently to many other species. There are also enough remaining specimens and recorded history to provide the necessary depth of understanding of the species’ past, and to plan its potential future in a responsible and effective manner.

In order to restore the passenger pigeon, it has been necessary to sequence the genome of a single individual and obtain high-quality specimens. The genetic diversity of the species has to be analyzed to assess both variable and fixed mutations between the passenger pigeon and its relative the band-tailed pigeon. Good quality samples have been acquired from collections at the Royal Ontario Museum and the Field Museum of Natural History.

To assist with the project, Brand enlisted the help of Harvard molecular biologist George Church, a pioneer of new genomic technologies. Church was sufficiently enthused by the idea to host a symposium at Harvard Medical School entitled “Bringing Back the Passenger Pigeon.” Church demonstrated his new genome-editing expertise, and the concept was embraced by other biologists and avian specialists.

"De-extinction went from concept to potential reality right before our eyes,” said Ryan Phelan, Brand’s wife, who also founded an early consumer medical-genetics company. “We realized that we could do it not only for the passenger pigeon, but for other species. There was so much interest and so many ideas that we needed to create an infrastructure around it. It was like, ‘Oh, my God, look at what we’ve unleashed.’ ”

The project did raise ethical questions, which were debated at a larger conference hosted by National Geographic some time later.
The event was attended by 36 of the world’s leading genetic engineers and biologists,including Sergey Zimov, who has created an experimental preserve in Siberia called Pleistocene Park, in which he hopes to re-introduce woolly mammoths. The loss of a species can impact and reduce the efficacy of an ecosystem, so the re-introduction of new species could have the opposite effect. Some people protest that reviving a previously extinct species is an attempt to "play God" but de-extinctionists argue that there will be solid benefits, and that the process is not dissimilar to the methods used in the development of pharmaceutical drugs, which are often derived from natural compounds in wild plants that were previously vulnerable to extinction. Those in favor of de-extinction also maintain that many extinct animals performed vital services in their ecosystems, which could subsequently benefit from their revival.

It may be a while before dinosaurs once again roam the earth, but this area of science has the potential to revolutionise the natural world. Preventing the extinction of endangered species must surely be an amazing and positive leap forward for both science and conservation, but the question remains as to what the impact could be on existing species if previously extinct creatures are re-introduced into the food chain.

What are your views? Would it be a good idea to bring previously extinct animals and birds back to life, or should we let sleeping dinosaurs and dodos lie safe in the history books?

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