Bring Back Your Dead: De-Extinction

Jurassic Park might be one of my favorite movies, but, sadly, the first thing to understand about the de-extinction process is that we're almost certainly going to be unable to bring back any dinosaurs. Their DNA is just too degraded. De-extinction (pretty self explanatory, just bringing back a species from extinction) is, if nothing else, one of the coolest projects science is embarking on- it's also, however, one of the projects most surrounded by questions regarding whether we should carry it out even if we can.

[Image source]

First off, we need to talk about how exactly de-extinction can be accomplished. First off is the Jurassic Park method- cloning. Cloning is by far the most glamorous of the main three methods suggested. It involves inserting a preserved cell nucleus into an egg from its nearest living relative, then implanted into that relative species to carry to term. This does, of course, require that the species does have a close living relative, which definitely takes quite a number of unusual species out of the running. We haven't yet successfully carried out de-extinction on an extinct species using this method, but it has been successfully carried out on endangered species before.

Next up is genome editing. Unlike in cloning, where the relative species is just carrying the embryo of the extinct species to term, in this one we're actually genetically altering the relative species to give birth to offspring of the extinct species. This one is the newest of the three main possibilities, and has only really become possible with the advent of increasingly more advanced gene editing technology, most notably CRISPR. Carrying this out, however, does require the DNA used to be in relatively good shape, just as with cloning- but it can get away with slightly more degraded sequences. (Dinosaurs are probably still out of the question, unfortunately.) For both this method and the previous method, we've begun storing huge amounts of gene sequences from endangered and extinct animals in gene vaults, out of the hope of reviving them.

The Pyrenean ibex, also known as the bucardo, was the first animal species to have survived de-extinction past birth. Unfortunately, the resulting baby ibex only lived seven minutes, and the other 207 attempts didn't even come all the way to term. The project has recently been restarted, however. [Image source]

Finally, we've got selective breeding. Selective breeding takes relatives of the extinct species, then tries to breed them into close versions of the extinct species. Most notably, this is being tried with the aurochs, extinct since 1627. Many breeds of European cattle are descended in part from aurochs, and scientists are attempting to breed them back into existence out of cattle, often by using fragmentary DNA retrieved from museum exhibits of bones. This has been tried multiple times before (including by the Nazis), but this attempt seems likely to bear the most success. Selective breeding, however, also has de-extinction's first true success story- the quagga. This extinct zebra subspecies was revived through selective breeding. It is technically classified as a new type of quagga, however, and not the old type brought back to life.

While it would be extremely cool to create parks filled with extinct creatures, it's far from the main reason it's being discussed. Right now, we're in the middle of a human-caused mass extinction, and it's a doozy. In fact, the only ones that beat it in the fossil record are the five great extinctions, including the one that wiped out the dinosaurs. Humans have, over the last few thousand years, wiped out countless thousands of species. Over the last couple centuries since industrialization started, however, those numbers have skyrocketed. The current extinction rate is estimated as being 100-1000 times the background extinction rate (the rate at which extinctions normally happen.) Over 10% of all species alive are threatened with extinction by the end of the 20th century.

The woolly mammoth is a prime candidate for de-extinction. It could be accomplished with either cloning or genome editing. This is because we have numerous, high quality samples of mammoth DNA, preserved in the flesh of frozen mammoths. [Image source]

So with such a severe extinction crisis going on, where are the objections to de-extinction coming from? Well, a few places. The first reason is simply a conviction that this is a waste of resources that could be diverted to preserving currently endangered species. This is really depressing, frankly, because implicit in the idea is that the little resources we currently have dedicated towards preserving endangered species aren't going to be increased at all in the near future. Still, it's not an argument entirely without merit- bringing a species back from extinction takes much more time, money, effort, and expertise than merely protecting a living one.

A criticism that concerns me more seriously has to do with how the de-extincted species will interact with their old ecosystems. If the species was wiped out by an invasive species, a lethal disease, or some other ecosystem altering threat, if that threat remains present in their old ecosystem, reintroducing them will just lead to them getting wiped out again. If they were wiped out by habitat destruction, they'd have to be introduced to new habitats, and could potentially act as invasive species themselves. These concerns are less worrisome when you're just bringing them back to put in a zoo (Holocene Park, anyone?), but there's also a real question there as to whether that's anything more than a vanity project to glorify our own brilliance. I personally think that there's a moral cost to extinction, and that merely bringing a species back is worth something, but it's certainly less than doing so and restoring it to its proper ecosystem.

The passenger pigeon, which once flocked in the billions, enough to darken the sky, were completely wiped out by human hunting in the 1800s, when they were commodified as a food source by Americans. The passenger pigeon is a candidate for revival by gene-editing, and there is in fact a currently ongoing attempt to do so. [Image source]

Unfortunately, de-extinction can only do so much. The current global biodiversity crisis isn't just a question of extinctions, but of biomass as well. Human activity, since civilization began, has cut the total biomass of Earth severely. Half of all plant biomass has been destroyed (bye bye, forests!) and wild mammals have been reduced in mass by 85%. Over 90% of all large bony fish have been harvested out of our oceans. Well over three fourths of the world's birds are chickens and other domesticated fowl. In fact, domesticated animals outweigh wild mammals by a factor of fourteen to one. Even restoring specific lost species in situations where it seems called for is only addressing a part of a terrifyingly huge problem.

There is a threat that I haven't discussed yet that de-extinction poses, and it's by far the scariest for me. (Well, there are a bunch more, but one in specific.) Namely, that fear is that the public might come to think that extinction is no longer scary or problematic, just because we can bring back a few species. Despite the promise of de-extinction, it will never be a viable replacement for simple species preservation to keep ecosystems at least relatively healthy. Like so many scientific developments, however, de-extinction seems like it might be a genie that's out of the bottle for good. There are several currently ongoing de-extinction projects, including some of the aforementioned ones, as well as some oddities like the gastric brooding frog. Sadly, though- still no dinosaurs. We're going to need a time machine for that.

If you're interested in reading more about the ongoing mass extinction, I wrote a series of posts on it a while back.

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Bibliography:

• The Sixth Extinction, by Elizabeth Kolbert
• The Ocean of Life, by Callum Roberts
• The Song of the Dodo, by David Quammen
• http://www.pnas.org/content/early/2018/05/15/1711842115
• https://www.nationalgeographic.com/magazine/2013/04/species-revival-bringing-back-extinct-animals/
• http://www.sciencemag.org/news/2016/09/should-we-bring-extinct-species-back-dead
• https://en.wikipedia.org/wiki/De-extinction
• https://en.wikipedia.org/wiki/Passenger_pigeon
• https://en.wikipedia.org/wiki/Holocene_extinction
• https://www.smithsonianmag.com/science-nature/these-are-extinct-animals-we-can-should-resurrect-180954955/