Sabre-toothed tiger (Smilodon fatalis)
Extinct: ~10,000 years ago
DNA preservation: 3/5
Suitable surrogate: 3/5
This fabled beast with its extraordinary canines would be a sight to behold. There are some spectacularly preserved sabre-toothed specimens from the La Brea tar pits in Los Angeles, but the tar makes extracting DNA tricky, so nobody has been able to isolate decent sequences. However, there are also some permafrost-preserved specimens that might be a better source of DNA. If we could obtain a genome, a close living relative of the sabre-tooth, the African lion, should be a good egg donor and surrogate mother. Californians, beware!
Neanderthal (Homo neanderthalensis)
Extinct: ~25,000 years ago
DNA preservation: 1/5
Suitable surrogate: 5/5
A draft sequence of the Neanderthal genome should be published sometime this year. "To have a reasonable-quality genome, say comparable to the chimpanzee, will then be another two years of work or so," says Svante Pääbo of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. While he and his colleagues hope the genome will offer unique insights into the differences between us humans and our mysterious cousins, there is speculation it could also be used to resurrect the Neanderthal. Because of our very close shared ancestry, humans would make ideal egg donors and surrogate mothers.
However, while Soviet scientists might once have tried to create a human-ape hybrid, today it is hard to imagine even the most crazed of mad scientists entering such taboo territory. "I find the idea of resurrecting the Neanderthal so ridiculous that any speculation on surrogate mothers is superfluous," says Pääbo. At most, researchers might replace some human genes with the Neanderthal versions in cells growing in a dish to see what the effect is, he says.
Short-faced bear (Arctodus simus)
Extinct: ~11,000 years ago
DNA preservation: 3/5
Suitable surrogate: 2/5
This towering beast would dwarf the world's largest living land carnivore, the polar bear. The short-faced bear may have been a third taller than the polar bear when standing upright, and it weighed up to a tonne. Recovering its DNA should be possible as there are specimens encased in permafrost. The short-faced's closest living relative is the spectacled bear of South America. The two species parted evolutionary company only around 5 million years ago, but unfortunately, at just a tenth the body mass of the short-faced bear, the spectacled bear is unlikely to be a particularly good surrogate.
Tasmanian tiger (Thylacinus cynocephalus)
Extinct: 1936
DNA preservation: 4/5
Suitable surrogate: 1/5
The last Tasmanian tiger or thylacine - an individual that has become known as Benjamin - died in Hobart Zoo in 1936. The existence of various preserved tissues less than a century old means geneticists should be able to get good-quality DNA and produce a complete sequence of the thylacine genome before too long. When it comes to resurrection, marsupials like the thylacine might be easier than most other mammals. Pregnancy in marsupials typically lasts just weeks, and a simple placenta forms only briefly, meaning there might be less risk of incompatibility between an embryo and a surrogate mother of another species. For the thylacine, the surrogate would be the Tasmanian devil. After birth, the fetus could be raised on milk in an artificial pouch.
Glyptodon (Doedicurus clavicaudatus)
Extinct: ~11,000 years ago
DNA preservation: 2/5
Suitable surrogate: 1/5
The Volkswagen Beetle-sized "colossal" armadillo, with its spiky, club-like tail, once rumbled across the South American countryside, and some might fancy seeing it do so again. Because there are no frozen glyptodons, obtaining usable DNA will depend on finding well-preserved remains in a cool, dry cave. Beyond that, there is an even bigger problem: the most suitable species to act as a host for a developing glyptodon embryo would be the far smaller 30-kilogram "giant" armadillo. The difference in size means it would struggle to carry its extinct relative to term.
Woolly rhinoceros (Coelodonta antiquitatis)
Extinct: ~10,000 years ago
DNA preservation: 4/5
Suitable surrogate: 5/5
Resurrecting the woolly rhino has lots going for it. As with the mammoth, there are plenty of specimens preserved in permafrost, and the availability of hair, horns and hooves is a big plus. These tissues can be cleaned up with shampoo and bleach to remove contaminant DNA from microbes and fungi before using enzymes to release an abundance of near-pure rhino DNA.
This makes it likely that geneticists will publish the complete genome of this hirsute beast before long. However, although the woolly rhino has close living relatives that might make suitable surrogates, all contemporary rhino species are themselves on the brink of extinction. As long as this remains the case, resurrecting a woolly rhino is unlikely to be a top priority.
Dodo (Raphus cucullatus)
Extinct: ~AD 1690
DNA preservation: 1/5
Suitable surrogate: 3/5
In 2002, geneticists at the University of Oxford got permission to cut into the world's best-preserved dodo specimen, a foot bone - complete with skin and feathers - held under lock and key at the university's Museum of Natural History. "It was one of the scariest things I've had to do," recalls Beth Shapiro, an ancient DNA specialist now at Pennsylvania State University.
This yielded minute fragments of dodo mitochondrial DNA but nothing more. Since then, no other specimen has yielded even a whiff of dodo DNA, but there is still hope that some will one day be found. "We're still looking," says Shapiro. If one turns up and a genome sequence could be produced from it, it would then be down to pigeons to help bring their famous cousin back from the dead.
Giant ground sloth (Megatherium americanum)
Extinct: ~8000 years ago
DNA preservation: 2/5
Suitable surrogate: 1/5
This giant stood around 6 metres tall and is estimated to have weighed a whopping 4 tonnes. The sloth's relatively recent extinction means that several specimens have been found with hair, an excellent source of DNA. So are we likely to see the giant sloth genome published? "Absolutely," says Hendrik Poinar of MacMaster University in Canada, who has extracted giant ground sloth DNA from fossilised dung deposited some 30,000 years ago.
The difficulty for anyone intent on resurrection would be the lack of a suitable surrogate. Its closest living relative - the three-toed tree sloth - is tiny by comparison. It might be able to provide eggs with which to create a giant ground sloth embryo, but the fetus would quickly outgrow its surrogate mother.
Moa (Dinornis robustus)
DNA preservation: 3/5
Suitable surrogate: 2/5
There is plenty of moa DNA to be found in well-preserved bones and even eggs in caves across New Zealand, so obtaining a moa genome should be doable. But which one? It would be tempting to go for the massive Dinornis robustus, which stood more than 3 metres tall, but starting with the more modestly sized Megalapteryx didinus might make more sense. Although only distantly related to ostriches, it might be possible to boot up the moa genome in an ostrich egg. As no bird has yet been cloned, however, perhaps the most feasible approach would be to engineer an ostrich embryo to be moa-like.
Irish elk (Megaloceros giganteus)
Extinct: ~7700 years ago
DNA preservation: 3/5
Suitable surrogate: 2/5
Deer-hunting enthusiasts would give almost anything for a chance to stalk this Pleistocene giant, once found across Europe. A typical male Megaloceros stood more than 2 metres tall at the shoulder and sported antlers 4 metres wide. It is actually a deer rather than an elk, and its closest living relative is the much smaller fallow deer, the two species having parted evolutionary company around 10 million years ago. The gulf between the two species means it is hard to see how a complete genome could be converted into a living, breathing animal.
Giant beaver (Castoroides ohioensis)
Extinct: ~10,000 years ago
DNA preservation: 2/5
Suitable surrogate: 1/5
There is fierce controversy over the reintroduction of normal beavers in some countries, so imagine how much fuss there would be over the reintroduction of the 2.5-metre-long giant beaver to North America. It's not too much to hope for a genome sequence of this massive rodent, says Hendrik Poinar, a geneticist at McMaster University in Hamilton, Canada. The capybara, which is about half the mass, would probably be the most suitable surrogate, though it might still be too distant a relative.
Gorilla (Gorilla gorilla)
Extinct: Almost
DNA preservation: 5/5
Suitable surrogate: 5/5
The first species to be brought back from extinction will most likely be one that is alive today. Conservationists are freezing tissue samples from some threatened species, so clones could be created with the help of a closely related surrogate species if a suitable habitat becomes available. For gorillas, the surrogate would be the chimpanzee.
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Ten extinct beasts that could walk the Earth again
Originally Posted by Linedoggie
Apparently a few do already exist in captivity
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