New technologies could make it possible to bring extinct species back to life, concludes a paper published on April 4 in the journal Science. These advances include back-breeding (assembling or reassembling an extinct species' genes), cloning and genetic engineering.
A leading candidate for de-extinction is the woolly mammoth. Russian scientist Semyon Grigoriev, of the Sakha Republic's mammoth museum, plans to replace the nuclei of an elephant egg with nuclei extracted from woolly mammoth bone marrow. The elephant would theoretically become a surrogate mother to a baby mammoth.
Tasmanian tigers died out in 1936, in part because they had little genetic diversity which translates to "bad news for a species," said Katherine Belov, professor of comparative genomics at the University of Sydney. "Species are less able to adapt to change." Even if Tasmanian tigers -- or other animals -- are resurrected, it will take some time to build up diversity again.
Louis Agassiz Fuertes, Wikimedia Commons
Experts believe billions of these birds populated the Americas when Europeans arrived. Loss of habitat and commercial exploitation of the birds for their meat are thought to have killed them all off.
Efforts are now underway to revive the species by extracting DNA fragments from preserved specimens, and later, using band-tailed pigeons as surrogate parents.
Joseph Wolf, Wikimedia Commons
The Pyrenean ibex, a horned mammal once common in Europe, was one of the first subspecies targeted for de-extinction. Scientists began the attempts in late 1990s, when the last female Pyrenean ibex was still alive. Even if researchers could successfully clone that individual, there would be no males for her to breed with. Instead, genetic engineering might be required.
Cicero Moraes, Wikimedia Commons
Since saber-toothed cat bodies are sometimes found frozen, it might be possible to extract preserved DNA and clone the animal. About 5 years ago, scientists did just that with a mouse that was dead and frozen for 16 years. Woolly mammoth remains are also sometimes found in a well-preserved, frozen state.
Oxford Museum of Natural History, Wikimedia Commons
The dodo, a flightless bird, proved to be a tasty meal for humans and other predators. In 2007, scientists found a remarkably well-preserved dodo in a cave. Dodo DNA could be used to resurrect this avian species.
University of Texas at Austin, Wikimedia Commons
Ground sloths, relatively slow, lumbering animals, were easy targets for prehistoric big-game hunters. Scientists have found remains that still bear soft tissue. As with woolly mammoths, there's a chance extracted DNA could be used to back-breed or clone the large sloths.
Charles Knight, Wikimedia Commons
The Irish elk has been extinct for 11,000 years. Like the woolly mammoth, it inhabited colder regions. As a result, bodies are sometimes found frozen and in relatively good condition, making them candidates for DNA extraction.
UNiesert, Wikimedia Commons
Earlier this year, Harvard geneticist George Church -- with tongue in cheek -- said that he was seeing an "adventurous female human" to be a surrogate mother to a cloned Neanderthal. While Church was really just theorizing about what it would take to bring a Neanderthal back to life, the possibility could be a reality, should any scientist undertake such a controversial project.
Paleontologist Jack Horner is leading a project to create a dinosaur out of a chicken -- a "dinochicken." He told Discovery News that birds "are dinosaurs, so technically we're making a dinosaur out of a dinosaur." He and his colleagues have been genetically engineering chickens to reactivate ancestral traits, such as long tails, which are more associated with non-avian dinosaurs.
Fewer than 250 adults may be left in West Africa, and those big cats are confined to less than 1 percent of their historic range.
The new study, detailed in the journal PLOS ONE, suggests that without dramatic conservation efforts, three of the four West African lion populations could become extinct in the next five years, with further declines in the one remaining population, study co-author Philipp Henschel, the lion program survey coordinator for Panthera, a global wildcat conservation organization, wrote in an email. [In Photos: The Biggest Lions on Earth]
The majestic lion once roamed throughout West Africa, from Nigeria to Senegal.
But as people have converted wild lands to pastureland, hunted the lion's traditional prey — antelopes, gazelles, wildebeest, buffalos and zebras — and gotten into conflicts with the animals, the big cat population has plummeted in West Africa.
Cash-strapped West African governments have put little money into lion conservation, in part because "wildlife tourism is quasi-absent in West Africa," Henschel said.
And research institutions have similarly neglected the region.
"Like wildlife tourists, most international research institutions and conservation organizations active in Africa also flock to the iconic game parks in East and southern Africa, meaning that lions faced a silent demise in West Africa over the past decades," Henschel told LiveScience.
To remedy that, Henschel and his colleagues recently completed a massive, six-year survey of West Africa's lions, using remote cameras, interviews with people and counts of lion tracks. The survey, carried out between October 2006 and May 2012, builds on a smaller study done last year, which found shrinking savannas for lions in the region.
About 400 adult and juvenile lions existed in the region. And the wild cats, which were originally thought to have inhabited 21 separate regions, actually exist in just four. Their range is now confined to pockets in Senegal, Nigeria and the borderlands between Benin, Niger and Burkina Faso.
These isolated populations are also threatened due to reduced genetic variation.
"Individuals are limited in their choice of mates, and end up reproducing with closely related individuals. Such inbreeding reduces the genetic fitness of sired offspring, which, in lions, manifests itself in lower reproductive success caused by lower sperm counts and higher rates of abnormal sperm in males," Henschel told LiveScience.
To keep the lion from going extinct in Africa, governments and conservation organizations should boost budgets for conservation parks and personnel, to keep people from killing the lions' prey or the big cats themselves, Henschel said.
The International Union for Conservation of Nature currently lists the lion as vulnerable in Africa. The West African lion is not considered a different species, so it is rated as regionally endangered, Henschel said.
But recent studies suggest the West African lions are genetically distinct from their brethren in other regions of the continent and are closely related to Barbary lions of North Africa and the few Asiatic lions left in India.
The genetic findings, combined with the dire survey results, suggest the West African lion should be listed as a critically endangered subspecies, or at the least, as a regionally critically endangered animal, Henschel said.
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