Can We Bring Back Extinct Species? Yes… and No

By Mikael Angelo S. Francisco

Contribution participating in the INPST 2018 Science Communication Awards contest.

Approximately 3,600 years ago, the last of the woolly mammoths took their final steps on the frosty soil of Wrangel Island, 140 km off the Russian coast. A small group of around 500 or so stragglers somehow managed to find their way to that isolated island, subsequently outliving their mainland counterparts by roughly 6,000 years.

 Asian Elephant - Richard Towell/Flickr; Woolly Mammoth - Wikimedia Commons
Asian Elephant – Richard TowellFlickr; Woolly Mammoth – Wikimedia Commons

The rest of the world’s mammoth population occupied the icy tundras of Europe, northern Asia, and North America. Sadly, they didn’t stand a chance against Earth’s warming climate and our ancestors’ frequent hunting. Meanwhile, scientists still can’t say for sure how the humongous, hairy herbivores of Wrangel were wiped out for good. One theory is that it may have been due to inbreeding, the passing down of “bad” genetic traits effectively sealing their fate. Meanwhile, others say that they met their end the same way their mainland cousins did — by the hands of both nature and man — only much later.

Understanding why the woolly mammoths died out is one thing. Bringing them back, however, is an entirely different story: one that’s inching closer and closer to reality.

The discovery of well-preserved mammoth remains across Europe has made genetic material from the behemoth more accessible. Paired with continued advancements in gene-editing technology, it’s becoming increasingly possible for the prehistoric proboscideans to make a comeback.

Indeed, the question of species de-extinction, also known as resurrection biology, is steadily becoming less about how to do it… and more about why.

From Dolly to de-extinction

When the world was introduced to Dolly the Sheep in 1997, she received abundant attention for being the first mammal cloned from an adult somatic (neither sperm nor egg) cell. By then, the caprine clone was a little over seven months old, the only survivor of a lengthy experiment involving 277 embryos. After seven years, Dolly died due to respiratory problems and arthritis — health complications said to be unrelated to her being a clone.

Dolly the Sheep - Paul Clements/AP; Pyrenean Ibex - National Wildlife Research Center;  Woolly Mammoth - Wikimedia Commons
Dolly the Sheep – Paul ClementsAP; Pyrenean Ibex – National Wildlife Research Center; Woolly Mammoth – Wikimedia Commons

Six years later, another milestone in genetics would follow: the first successful (albeit short) attempt to bring a dead species — specifically, the Pyrenean ibex — back to life. Scientists from France and Spain implanted genetic material from Celia, an ibex that died in 2000 after being crushed by a fallen tree, into domestic goat eggs, resulting in one clone being born alive out of 208 embryos. Unfortunately, its defective lungs robbed it of its life several minutes later.

Both Dolly and Celia’s “child” are examples of somatic cell nuclear transfer, one of the three main methods of de-extinction. As the process involves infusing an enucleated (nucleus-free) egg cell with a nucleus from a donor cell, it requires genetic material extracted from a living individual. Thus, it’s a long shot for species that have been extinct for a considerable period of time, such as the dinosaurs, to be resurrected using this method.

“With current technology, DNA samples only remain useful for about 1 million years,” explained Beth Shapiro, an evolutionary biologist from the University of California, Santa Cruz (UCSC), in a 2015 interview with Smithsonian Magazine. “So theoretically, we could clone a Neanderthal, but not a Triceratops last seen 65 million years ago.”

In the case of woolly mammoths, biologists are exploring a different avenue for de-evolution: genetic modification. By studying available DNA samples, scientists can figure out precisely what makes a mammoth a mammoth. With that data, they can create a genetic blueprint, which they can use alongside CRISPR and other molecular tools to edit the genomes of mammoths’ closest living relatives, Asian elephants. The end result? A hybrid that is neither true elephant nor true mammoth, but close enough to the extinct animal. Think of it as a sculptor swapping out parts of a finished statue with fragments from a broken one, in order to make the former look as identical to the latter as possible.

The third technique, known as “breeding back,” involves the selective breeding of an extinct animal’s living relatives or descendants, in order to spawn offspring with the dead species’ distinctive traits. Current efforts to revive quaggas, aurochs, and dire wolves are anchored on this method.

Righting wrongs vs. playing God

The bigger challenge, however, lies in determining which species to resurrect — and perhaps more importantly, the rationale behind doing so.

In a 2016 paper, ecologists from the University of California, Santa Barbara (UCSB) proposed three simple guidelines for choosing which species to give a second shot at life: Pick a species that (1) fulfils a unique role — in other words, a function that only one or two species can provide — in the ecosystem, (2) was only recently wiped out, and (3) can realistically increase in population enough to resume the role it left behind.

Researchers such as Harvard University’s George Church believe that reviving the woolly mammoth could help us mitigate the effects of climate change on the planet. In an article on Science Magazine, Church explained that the species’ return could shift the landscape “back toward the grasslands,” as during the Pleistocene, mammoths and other herbivorous megafauna were crucial in spreading seeds via excrement and sustaining plant life across the land. Additionally, by stomping through snow and enabling cold air to pass through, mammoths could curb the meltdown of Siberian ice, preventing the release of tons of greenhouse gases into the atmosphere.

De-extinction techniques could also enable us to imbue endangered species with improved genetic diversity, giving them a better shot at survival. Genetic diversity is basically what allows species to cope with changes in their environment; members of that species equipped with the necessary characteristics for survival will likely pass those traits on to their offspring, increasing future generations’ chances to thrive.

However, while it may appear to be a perfectly good concept on paper, de-extinction isn’t without its issues.

As mentioned earlier, choosing which species to bring back is far from a walk in the park. UCSB ecologist Douglas McCauley cites the lesser stick-nest rat, which was officially declared extinct in 2016, as an example of a species that deserves more attention from de-evolution researchers. The large stick nests it built across central Australia, explained McCauley, served as biodiversity hubs for the local fauna. Compared to the mammoth, it’s a lot less impressive, but no less important.

Another challenge lies in the rather high mortality rates of cloned or reprogrammed animals, owing mainly to the “genetic memory” possessed by the donor cell’s nucleus. This creates an incompatibility of sorts with the new genetic material, resulting in physical deformities and other biological “errors” that reduce the animals’ chances of survival.

Perhaps the biggest concern that comes with de-extinction, however, is a potentially diminished regard for species conservation. “Honestly, the thing that scares me most is that the public absorbs the misimpression that extinction is no longer scary,” said McCauley. “That the mindset becomes: Deforest, no biggie, we can reforest. If we drive something extinct, no biggie, we can de-extinct it.”

Restore what was lost… or save what’s left?

It’s worth noting that the resurrection of an extinct species in its purest, “uncontaminated” form isn’t really possible.

“If you’re willing to accept something that is an elephant that has a few mammoth genes inserted into its genome and therefore is able to make some proteins that mammoths might, we’re probably closer to that,” Shapiro clarified.“If you mean 100-percent mammoth, with all mammoth genes and behaviors, that will never happen.”

Whether or not resurrection biology makes the full restoration of extinct species possible, humanity’s takeaway shouldn’t be that the results of our irresponsibility are easily reversible. In fact, more than anything else, the prospect of de-extinction should highlight the frightening possibility of a future full of nothing but genetic copycats.

References:

Keywords: woolly mammoths, advancements in gene-editing technology, species de-extinction, resurrection biology, Dolly the Sheep, genetics, Pyrenean ibex, Celia, somatic cell nuclear transfer, genetic modification, CRISPR, breeding back, cloned or reprogrammed animals, species conservation.


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