Colossal Biosciences, a company mainly known for intending to genetically engineer proxies for several iconic extinct species, announced this week that it has made major steps towards the de-extinction of the thylacine, or Tasmanian tiger.
The thylacine was a carnivorous marsupial that was declared extinct in 1936, after decades of hunting and habitat loss. In a press release, Colossal reported that its reconstructed thylacine genome is about 99.9% complete, with 45 remaining gaps they aim to close through further sequencing in the coming months.
Last year, a team of researchers unaffiliated with Colossal recovered RNA from a thylacine—a first in an extinct species—for the first time, for which they earned recognition in the Gizmodo Science Fair. In the recent Colossal release, the company stated it was able to isolate long strands of RNA from a 110-year-old thylacine specimen preserved in ethanol.
Colossal declared in 2022 that it would attempt to “de-extinct” the thylacine; since no living thylacines exist, de-extinction actually refers to the creation of proxy species for the original animals. Proxy species are, for all intents and purposes, replacements; they will never be 100% thylacine, or mammoth, or dodo, but will be engineered to look the same and function in the same environmental niche. That’s right: Another part of Colossal’s plan is to “re-introduce” these proxy species to their habitats, or the closest modern thing to them.
The thylacine is often referred to as the Tasmanian tiger or the Tasmanian/marsupial wolf, despite tigers and wolves being felines and canines, respectively, while the thylacine is closely related to neither. It was the sole member of its genus, Thylacinus cynocephalus. To de-extinct the animal, the company plans to genetically edit the cells of a fat-tailed dunnart, the thylacine’s closest living relative, into the nearest thing they can get to the Real McCoy.
Though the reconstructed genome is estimated to be nearly perfect, there are some genetics that are lost to time, as was the case for the extinct Christmas Island rat, which a different team of researchers used as a case study in prospective de-extinction. A member of the team, who is now a member of Colossal’s advisory board, told Gizmodo in 2022 that “the world doesn’t need any more rats” and “the money it would take to do the best job possible could be spent on better things, e.g., conserving living things.” Some ethicists and other experts argue that even if it looks, walks, and yips like a thylacine, that doesn’t mean Colossal has truly de-extincted the animal, which was overhunted by humans after being scapegoated for attacks on Tasmanian livestock.
Earlier this year, Gizmodo sat down with Beth Shapiro, the company’s chief science officer, to discuss Colossal’s plans, timelines, and the challenges and ethics of de-extinction. A month before, Colossal announced that it had engineered elephant stem cells—a useful tool for the company’s ambition of creating hairy, cold-resistant Asian elephants—a 21st-century facsimile mammoth.
In a release announcing the new genomic milestones, Colossal co-founder and CEO Ben Lamm said that the team is “pushing as fast as possible to create the science necessary to make extinction a thing of the past.”
But Colossal is also working on the genomes of extant species, like that of the northern quoll. In the same release announcing the genomic milestones concerning the thylacine, the company stated that it improved the quoll’s resistance to toxins from the cane toad. The cane toad is an invasive species introduced to Australia in 1935 (a year before the thylacine’s official extinction) to control pests; unfortunately, the toads also eat, and are toxic to, many native species.
“By changing a single base in a 3-billion base pair genome, we can make the endangered northern quoll go from completely susceptible (lethal) to cane toad toxin, to among the most resistant species to this toxin on earth,” said Andrew Pask, a member of Colossal’s Scientific Advisory Board and a researcher at the University of Melbourne’s Thylacine Integrated Genomic Restoration Research Laboratory (or TIGRR Lab), in the same release.
Colossal has its hand in multiple cookie jars right now; the company is clearly making progress in what we’re capable of when it comes to gene editing. And as Ross MacPhee, a disapproving mammalogist at the American Museum of Natural History, told Gizmodo last year, there will be “manufactured organisms” in the next decade.
Whether the company heeds the lessons of the past—using cane toads to change the environment, for example, just for them to do so deleteriously—is another question, and one that may ultimately be proved out in the forests of Tasmania.
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