De-Extinction: Can we bring back the wooly mammoth? The dodo? America’s iconic passenger pigeon and Australia’s Tasmanian wolf, the thylacine?
Scientists have been asking this question since the discovery of DNA in the latter half of the 19th century. But it wouldn’t be until Steven Spielberg’s thrilling film adaptation of Michael Crichton’s Jurassic Park that the idea of de-extinction would take public imagination by storm.
And almost three decades on, the science-fiction of Jurassic Park is quickly becoming science-fact. But thankfully, the focus of our real-life biologists and entrepreneurs alike is on herbivores like dodos and wooly mammoths. Because if Jurassic Park taught us anything – it’s to let history’s T-Rexes, raptors, and their carnivorous cousins remain very extinct.
But what is de-extinction? And between all this talk of bringing back mammoths, dodos, and pigeons, is it truly possible?
The short answer? Yes, de-extinction is 100% viable science that is fully underway. But not in the way one might expect.
De-extinction (also called resurrection biology) is the process of resurrecting species that have died out, or gone extinct.
Rather than being one straight-forward path to revival as JP‘s animated Mr. DNA illustrates, however, the modern science of de-extinction encompasses three different fields of science altogether.
Broadly speaking, there are three approaches to de-extinction:
- Genetic engineering is as Jurassic Park foretold. To do so, geneticists must sequence the genomes of an extinct animal’s DNA completely. JP used the DNA of modern frogs to fill in missing base pairs, or building blocks of DNA, which remains fiction. Instead, the sequenced DNA of the closest living relative (which would be birds for dinosaurs, and elephants for mammoths) is where scientists are looking.
- Cloning is another option. As Dolly the sheep’s saga showed us in the 1990s, cloning has been on the table for decades. But this will never be possible for extinct animals unless a fully preserved cell or full set of chromosomes is discovered for the specific de-extinction.
- Back-breeding is the selective breeding through generations to produce something similar to the extinct animal. Think dog-breeding for de-extinction purposes, where instead of mating canines to produce specific traits, scientists would genetically alter, then breed modern descendants (elephants) of the extinct animal (mammoths) to produce something akin (hairy) to their bygone ancestor.
Back-breeding, specifically, is one option when it comes to mammoth de-extinction, as the extant Asian elephant is a close-living relative. But it’s genetic engineering that fuels the hopes of Colossal, the company that recently funded Harvard geneticist George Church an appropriately-mammoth $15 million to “resurrect” the species. In fact, Colossal plans to birth a mammoth-elephant hybrid through a mixture of genetic engineering and surrogate back-breeding by 2027.
Genetic engineering, as Michael Crichton highlighted in his original Jurassic Park novels, is also on the table for other de-extinction candidates like Australia’s “Tasmanian wolf” – the marsupial thylacine – which went extinct recently enough for preserved specimens to still be near-completely intact.
Genetic Engineering Could, In Theory, Revive Any Extinct Animal With Enough Extant DNA
To take the genetic engineering approach to de-extinction, scientists must first have extant (still existing) DNA for the extinct animal. In truth, scientists will need almost-to-near-complete sequencing of the animal’s genetic code.
In the case of the thylacine, a team of scientists led by the University of Melbourne’s Prof. Andrew Pask were able to do so in 2017.
“We had one of the [thylacine] babies from the Melbourne Museum that was a baby taken from a mother’s pouch and dropped straight into alcohol,” Professor Pask tells Australia’s ABC News.
Because of this baby’s swift preservation, Pask’s team was able to sequence what was then the most intact genome for an extinct species. Doing so proved vital because, as animals die, our DNA fragments – decaying and breaking up into shorter strands. And the more deteriorated the DNA, the more likely it is to be found in countless jumbled pieces.
University of Copenhagen’s genomics researcher, Tom Gilbert, compares it to piecing a shredded book back together without an intact, identical book to reference:
“Let’s say that before I give you the [book] I put it through a shredder and all you have are fragments of maybe three to 30 words long,” Prof. Gilbert says. “And [then] I ask you to tell me what’s going on.”
More plainly, it’s like trying to rebuild an exact story with a bunch of random sentences. But de-extinction-curious scientists now believe they have a cheat code: the DNA of an extinct species’ closest living relative.
Enter an Animals’ Closest Living Relative
For Australia’s marsupial thylacine, that closest living relative is the much smaller numbat:
Around 95% of the numbat’s DNA is shared with the thylacine, something we know thanks to the tireless work of DNA Zoo Australia, based at the University of Western Australia. Recently, their team completed a “chromosome-length 3D genome map” of the numbat.
Their focus? “To build the base which will enable the genetic rescue of existing species,” says DNA Zoo Australia director Dr. Parwinder Kaur, adding the process of de-extinction will, she believes, “become a very routine thing in the next decade or so. I can see around me the technology on de-extinction is advancing so fast.”
And Professor Pask, too, believes it will be a matter of when – not if – for thylacines, passenger pigeons, and even mammoths. All thanks to DNA.
“At the moment we’re looking to understand the scope of all the edits we’d have to make for our surrogate animals,” he adds. “I’m fully confident that we will get there. We definitely have all the technology at hand. It’s just that it would take a very long time to do it at the moment.”