De-Extinction: Return of the Endlings?

This blog has looked at the extinction and extirpation of many species and admittedly, has been fairly pessimistic. However, it has yet to consider the growing phenomenon of 'de-extinction', perhaps there is room for a little optimism? Is this a realistic approach to conservation or is it a load of Jurassic Park wannabe nonsense? The idea based on using preserved or "ancient" DNA from several individuals of an extinct species and creating clones of each of them, we would be able to create a new and viable population of that species. There are cryo-zoos, such as the one in San Diego, which store frozen DNA of extinct species with the potential to form these clones. Much of the attention given to, and work within, de-extinction focuses on this cloning aspect, but other researchers have attempted to work through selectively back breeding a species from its genetically similar living descendants.

De-extinction efforts have already been made for many species that we have seen recent endlings of, such as the passenger pigeon, the Pyrenean ibex and the Tasmanian tiger, whereas some scientists are working on much older animals such as the woolly mammoth. However, 60,000 years is effectively the age limit for use of DNA, so dinosaurs won't be happening any time soon. The first de-extinction in history was the Pyrenean ibex, which was done in 2009 by creating a clone egg using the DNA of Celia, the (formerly) last ibex, which was taken shortly before she died in 2000. Unfortunately, the ibex was short lived and died within 10 minutes but scientists are planning to reattempt when cloning techniques have improved. This attempt, in itself, was an improvement on previous attempts in 2003 which had failed to produce an egg capable of surviving the full gestation period. Significant progress has also been made for the passenger pigeon, where DNA has been preserved in museum specimens. Unfortunately the DNA of these specimens is contaminated and fragmented due to the way they have been preserved and kept, as oppose to the ibex DNA which was stored in liquid nitrogen. However, it is still possible to reconstruct the genome by synthetic hybridisation of the DNA fragments with the genome of its closest living relative, the band tailed pigeon, which scientists are currently working on. This would then be used to create cells which contain passenger pigeon genes, which would then be injected into band-pigeon embryo with the goal to create a band pigeon which lays passenger pigeon eggs and acts a surrogate parent for it.

National Geographic cover of de-extinction issue; Source.

Since 2013, a team of scientists from South Korea and Russia have been working on the de-extinction of woolly mammoths.  There have been difficulties as although mammoths have been found well preserved, their DNA has not been intact enough to produce viable embryos for a clone based de-extinction. Alternatively, a second method has been investigated which involves the artificial insemination of elephant eggs with preserved woolly mammoth sperm. The elephant-mammoth hybrid offspring would be able to be cross-bred over several generations to produce near pure mammoths. Again, this has been unsuccessfully due to mammal sperm cells lose their potency after over 15 years in freezing. The major problem has been finding usable DNA, blood recovered from the 2013 carcass provides an apparently good chance of successful cloning - we will have to wait and see. Others are pursuing different routes to restoring the mammoth, Harvard geneticists are working on migrating components of the mammoth genome into the Asian elephant genome in order to create viable hybrids. Adrian Lister, a renowned mammoth expert, highlighted that there is a lack of suitable habitat remaining for any resurrected mammoths and that, as highly social animals, they would suffer from existing in very small numbers. However, a Pleistocene rewilding experiment known as 'Pleistocene Park' (not joking), could provide refuge for the mammoths and would also benefit from the grazing herd behaviours in recreation of steppe. Interestingly, Pleistocene Park also aims to prove that it was not climate change but over-hunting and other human interferences that lead to the disappearances of these grasslands and associated species during the Pleistocene. This could be a exciting new evidence in the debate surrounding the Pleistocene megafaunal extinctions.

Pleistocene Park in Siberia; Source.

As mentioned earlier, selective back-breeding from the closest living relatives of animals is another option for potential de-extinctions. This is being done for aurochs in Europe, based on genetic material taken from bone and teeth fragements. The last European aurochs were lost in 1627 after a long history of over-hunting and exploitation, but their descendants (most modern cattle breeds) are abundant throughout Europe. The genetic material provides a goal, so that cattle can be bred to try and reach as close to the original aurochs as possible, both phenotypically and genotypically. Early attempts resulted in the created of a new breed, Heck cattle, which are at best vague-lookalikes. Currently there are two projects, the TaurOs Project and the Uruz Project, which are competing to resurrect a true, or atleast very close to, aurochs within the next 20 years. Earlier this year, it was proposed that there could be the potential to bring back Lonesome George, or at least a genetically very similar species, by a breeding programme rather than cloning. Even if the animals themselves are clones, captive breeding, which has proved successful in many conservation efforts, will be a major part of de-extinction.

So, whilst it seems that de-extinction is scientifically possible, the bigger question is rather, should we actually be doing this? Proponents of de-extinction such as Stewart Brand would argue that we have the ability and the moral obligation to repair the damage we have done, so there is no excuse not to. Others such as Adrian Lister would say that efforts and resources should be focused on conserving currently endangered extant species. The lack of suitable habitat is also a concern for many species. I feel that whilst there is certainly value and appeal in resurrecting species and "righting our wrongs", it must be done carefully and must not detract the need for conservation efforts to currently endangered species. This is not an alternative to conservation. This is an unfortunate second best to not having lost the species in the first place.