Look Who's BackExtinct animals could walk among us once again. Aisling Brennan looks at the pros, cons and some of the difficulties involved.[br]WHAT if, within your lifetime, you could go to a zoo and see a mammoth? Leaving aside the pseudo-scientific warnings of franchises like Jurassic Park (dinosaurs are out of the question anyway), this seemingly ridiculous concept could actually be feasible, as science continues to push the impossible. The real questions are: what can we bring back, and should we even try in the first place?Mammoths are top of the list, they’re huge, iconic creatures that keep turning up frozen in permafrost, and their closest living relatives are the Asian elephants. Other prime candidates haven’t been extinct for quite as long as the mammoth, so their genetic material is likely to be of better quality, and their natural environment is not so far removed from those found on the planet today.Imagine flocks of passenger pigeons, beautiful Carolina parakeets, and giant 12 foot tall Moa species. Herds of aurochs, mammoths, or woolly rhinoceri. Populations of the biologically fascinating gastric-brooding frogs (which stored their fertilised eggs in their stomachs until they hatched). These are all goals of some of the world’s leading scientific minds. Tasmanian wolves, Pyrenean Ibex, even the dodo, are also all relatively high on the list of potential candidates, although that list could theoretically span a huge variety of species.As incredible as some of these concepts are, and the recent breakthroughs in genetics and related fields, the truth is that full de-extinction of any species is still a decent way off. Not to cast too negative a shadow on the dream, but there are a vast number of obstacles to be overcome.First up is getting useable genetic material, which can be tricky when species aren’t around anymore. Not much is needed, theoretically you could get an entire genome from a tissue sample smaller than a pinhead, but the best sources are preserved soft tissues, like skin, muscle or feathers.Second, most suggested methods for de-extinction require a closest living species for things like filling genetic gaps or acting as sources of genetic diversity or surrogate parents. This raises many ethical questions as well as practical ones: Where to find a modern related bird large enough to lay a moa egg? How can the Sumatran rhinoceros act as a source of woolly rhino genetic diversity when it itself is critically endangered? Not to mention the possibility that older species may require plant, pollinator, or symbiotic fungi species that are themselves extinct, as well as particular habitat conditions to live and thrive.Ethics are a whole other bag of extinct fish, both in terms of grand ideological philosophies, and practical science. For example, with mammoths, the concept of implanting a mammoth-elephant hybrid into the womb of a female Asian elephant is unsavoury to animal rights activists as well as geneticists. A lot can go wrong, even with science we are pretty certain about. A relatively recent effort in 2009 to clone a Pyrenean Ibex from frozen DNA resulted in a newborn calf that sadly only lived for seven minutes.Many people also adopt a “Life finds a way” approach towards de-extinction as a concept, believing it’s something that we ought not to meddle with. Though there are several more concrete arguments that people have for and against the idea.One of the main debates within this battle is the idea of ‘hope vs waste’. Those in favour of de-extinction as an avenue of research argue that the long-term products could re-inspire hope and interest in the fields of conservation as well as zoological institutions worldwide. Entrance fees from zoos provide a surprising amount of conservation funding, and inspiring enthusiasm for wildlife and environmental protection is always a societal boon. Furthermore, collections of natural specimens could become treasure troves of genetic material, and museums all over the world would receive renewed interest and investment.On the other hand, some say that investing in such research is a ‘waste’ given how many thousands of species are currently endangered. They also say that pushing a message of ‘we can fix what we’ve destroyed’ could actually hinder conservation efforts if political or industrial figures believe that there is no point protecting an endangered species if we can resurrect them later. Even some within the scientific community are sceptical, fearing that if research priorities shift, resources, positions and facilities could be stripped from those working in the field rather than in a lab.However, while some label the concept a ‘distraction’, the lofty goals of species resurrection are only the beginning for some working on the problem. Some animals like mammoths or European aurochs (cattle, extinct since 1627) were keystone species in their environments, being dominant grazers, and massively affecting their surroundings. The disappearance of mammoths, from what was once the largest biome on earth in the far north, has been hypothesised as a driving force behind its convergence into the modern species-poor tundra and boreal forest we know today.The return of such prominent grazers could see the increase in carbon-fixing grasses and alter greenhouse-gas-emissions from an entire hemisphere. Other extinct keystone species include the Passenger pigeon, which spread fruit and seeds far and wide across its vast range. And the return of iconic species like the Tasmanian wolf could help protect lands that are currently under pressure from loggers and other exploitative industries.Actual functioning populations of now-extinct animals are a long-way off, but even the journey has its potential benefits. Genetics is such a universal and fast-evolving area of research that any breakthroughs in particular projects goes on to have concrete impacts and applications in everything from medicine to agriculture. Furthermore, most of the scientists working on the de-extinction conundrum believe that research in extinct animal genomes could drastically affect how we look at and deal with conservation.Tiny populations in a doomed genetic bottleneck could have their DNA diversity restored, and genetic ‘Achilles heels’ could be cured in just a few generations. Anything we learn from extinct organisms can go on to directly impact their modern descendants. Even UCD is involved in research on getting viable genetic material from museum collections, which itself could have impacts in labs the world over. So the argument could be made that the journey is far from a ‘waste’.Whether fought in terms of ethical, legislative, or scientific battlegrounds, the concepts surrounding de-extinction (and the arguments for and against them) have captured some of the most brilliant minds on the planet, and will likely go on to inspire many-more. And while the jury is still very much out on the matter, if someone cites Jurassic Park as a proper cautionary tale, chances are they don’t know what they’re talking about.