In May 2013 Russian researchers found a perfectly preserved woolly mammoth carcass frozen in the ice on an island off Siberia. As if it were pulled straight out of a meat locker the animal's body still had red, fresh muscle tissue and -the real prize- liquid blood. The female mammoth had been laying there like Snow White in her class coffin for four thousand to ten thousand years before the Russians came excavating, bringing with them the hope that she might live again to feel the sun on her shaggy brow.

Scientists have cracked much of the mammoth's genetic code from preserved hair, but the potential to clone the animals isn't possible without living cells. And this mammoth is currently being examined for just that. But even if the scientists don't find any viable cells in their specimen, there is more than one way to skin a mammoth, and one way or another humans now have the technology to bring animals back from extinction.

Sort of.

(Intro)

The concept of bringing extinct species back from the void has titillated scientists long before those crafty velociraptors jiggled door knobs in Jurassic Park. It's called 'de-extinction' or, if you're feeling more poetic, 'resurrection biology', and it's a real hot topic nowadays.

So let's cut to the chase: will you ever get to feed a baby stegosaurus?

No. Sorry.

While Jurassic Park got some things right, there are some major biological limitations to resurrecting extinct species. DNA naturally degrades over time and you need some intact genetic material to reconstruct the genome. Scientists recently determined that DNA can remain intact for no more than about 6.8 million years. Not bad, but dinosaurs haven't been around for about 65 million years. So, for better or for worse, you will never have to escape a velociraptor. Instead, the only vanished species that we can attempt to revive are the ones that died relatively recently, within the past few tens of thousands of years. Which is really kind of fitting considering that's the very same time frame in which humans got serious about hunting and expanding and general domination.

Many proponents of de-extinction think that, if these species were driven to extinction at the hands of humans, then it's our moral obligation to restore them if we can. So, how exactly would you resurrect a vanished species?

Well, there are currently three possible methods: cloning, genetic reconstruction, and back-breeding.

In 2003 French and Spanish scientists did bring back a dead species to life. For like ten minutes. The Pyrenean Ibex, a type of wild, large goat with majestic horns also known as the bucardo, once climbed among the mountains between Spain and France until it was hunted to extinction by the late 1990s. Scientists used frozen cells, collected from the last known bucardo, a female named Celia, to create a new embryo through the nuclear transfer method of cloning, which was perfected by the people who gave us Dolly the sheep, the first mammal cloned from an adult cell back in 1996. Researchers injected nuclei from the bucardo cells into goat eggs that had been stripped of their own DNA, and then implanted the eggs into living mama goats.

In nearly sixty attempts only seven lady goats got knocked up, and only one carried her clone baby to term. Sadly, the newborn came out with deformed lungs and didn't survive. Still, in terms of bringing an extinct animal back to life those scientists had way better genetic material to work with than the average de-extinction lab.

Let's say you want to clone something that isn't newly extinct like the bucardo. Say, a woolly mammoth. Researchers have already found a decent payload of mammoth parts: bone, marrow, hair, skin muscle tissue, fat, and that blood I mentioned.

The ideal cloning scenario starts with finding an intact, frozen cell. The last mammoth went extinct nearly four thousand years ago, and permafrost does a decent job of preserving genetic material compared to, say, the tropical island where dodos last nested. So it'll be a lot easier to scrounge up material to make a mammoth than a dodo, but most scientists doubt that an animal cell could survive several millennia under the Siberian tundra.

Still, for the sake of exercising the imagination, say they did a genetically viable mammoth cell. You can remove the nucleus of this cell and transfer it into a hollowed out elephant egg, since elephants are the mammoth's closest living relatives. But then there's another problem. Elephants only ovulate every five years, and to get the eggs you have to navigate a reproductive tract that's three meters long. This makes egg extraction from elephants... hard, to say the least. And it could require hundreds of eggs to create one viable offspring, so again, we have to assume that we overcome that hurdle.

So if the mammoth's DNA is healthy enough, it could take command of an elephant egg, and with the help of a little chemical or electrical boost the cell would start dividing. From there you just gotta put on a little Barry White and implant the egg into a surrogate elephant's womb, and after nearly two years of gestation, you've got a baby mammoth. Maybe.

But, in the absence of the viable cells or nuclei required for cloning, scientists have another path to bring back host species: genetically reconstructing a genome. This new DNA-technology is cutting edge and requires only fragments of broken genetic material from hair, horn, fur, or feather, things that you can often just find from museum specimens. You basically just sequence and line up the DNA of extinct species, say, a passenger pigeon, and compare it to the DNA of closely related existing species, like a common pigeon, a rock dove. After comparing the two, you essentially start cutting and pasting, substituting chunks of passenger pigeon DNA into the cells of the common pigeon's. The resulted hybrid stem cells could be coaxed into egg and sperm cells, and then used in cloning. Eventually you end up with a living bird with enough passenger pigeon DNA to pretty much be a passenger pigeon.

Another lower tech and very slow method to restore extinct species is to back-breed it. Back-breeding is kind of like reverse-engineering evolution. Much in the way that dog breeders work out particular traits like body shape or coat color, back-breeders look to the past to bring out all the ancestral genes in an animal.

Take something like the aurochs, an ancient, wild, cow-like beast formerly found in Europe and Asia. Researchers know some of the aurochs' genes are still swimming around in certain cattle strains, kind of like humans have one to four percent Neanderthal DNA in their blood. The European TaurOs Project has identified some of these aurochs genes in existing cattle breeds and is selectively breeding them to bring out those ancient traits. Over the course of multiple generations they hope to produce a breed that would be a close match to the aurochs and, ultimately, introduce it into the wild.

In theory, like crazy insane theory, you could even bring back Neanderthals the same way. Although since it takes between one and two decades for a single human generation to reach sexual maturity, this much breeding would take a long, long time. And also, as previously mentioned, it would be totally like, immoral. And wrong. And crazy.

Which brings us to the potential problems with resurrection biology. Like, for one, would these test tube clone babies be a bunch of inbred, hybrid weirdos? Critics of de-extinction worry that resurrecting species would suffer from poor genetic variation. Like, if scientist created twenty identical great auks from a single egg, there wouldn't be enough genetic diversity to usher in a viable, new population. After all, bringing to life one individual does not constitute the restoration of a species. And even if you do manage to create a gaggle of great auks, where would you put them if there's no habitat left for them?

It comes down to the question of where and how they will live. Most species we're even capable of resurrecting were initially driven to extinction at the hands of humans. But if current policy won't allow for a living species, bison for example, to freely roam its original Great Planes habitat, or if African farmers worry about rampaging elephants, who's realistically going to welcome woolly mammoths into their backyard? And who's gonna teach those first mammoths how to be mammoths? What will they eat? How will they act? How will they learn? Do you think that they're gonna be elephants putting on shaggy coats and moving to Siberia? The whole concept is a big Pandora's box, and critics also worry that domino effects may spring from reintroducing extinct species to landscapes that they've been away from for too long.

Would passenger pigeons really be more like an invasive species that might out-compete existing birds, and if their numbers approach the sky-blackening proportions that they used to, would New Yorkers be cool with their fancy shoes getting soiled by sogging through so much bird poop? These are all things we need to think about before we throw a lot of time and money in this kind of research, but on the pro-side fans of de-extinction point out that resurrection biology has multiple awesome applications.

This kind of technology could help preserve and bring back from the brink of extinction vulnerable living species for instance which in itself could make it worth developing. And it offers a lot of learning opportunities to be found in dead species. You know, we've already revived at least one life form for educational purposes, the notorious 1918 Spanish influenza virus that slaughtered perhaps fifty million people back in the day. In 2005 researchers from the Centers for Disease Control and Prevention cloned the killer in order to study it, and we've since learned a lot about how that flu evolves, spreads, and so efficiently kills. This is potentially vital information that could help us prevent future epidemics. 

Another argument for de-extinction has to do with filling ecological niches. When a species is eliminated from its natural environment it leaves a void that could have far-reaching effects. Some de-extinction proponents fantasize about correcting ecosystems like the arctic by reintroducing mammoths who once helped maintain the permafrost layer by knocking down trees and allowing grasses to flourish. We're just starting to realize how important it is to preserve permafrost, since its melting releases an incredible amount of methane into the atmosphere. The thought is mammoths on the landscape might help with that kind of natural regulation.

And finally - it's just cool! Just admit it: the thought of watching the giant ground sloth grazing in the real world, in real life, with your eyes, that's exciting!

So once again our technological capabilities have shot beyond our capacity to fully understand their implications. However you personally feel about bringing extinct species back to life, and all that comes with it, know that it is no longer a question of 'Can we?' but rather a matter of 'Should we?'

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