Meet the Scientists Bringing Back the Extinct Tasmanian Tiger
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This week, the biotech/genetic engineering company Colossal – co-founded in 2021 by renowned geneticist Professor George Church and serial entrepreneur Ben Lamm – announced it has begun a de-extinction project of the thylacine – an Australian marsupial commonly referred to as the “Tasmanian tiger”. The announcement follows Colossal’s recent success in raising over $15 million to de-extinct the woolly mammoth.
"Team Thylacine", consisting of Ben Lamm (far left), Professor Andrew Pask (center) and Professor George Church (far right). Credit: Colossal Biosciences.
The thylacine – a slender “fox-faced” creature – was the largest carnivorous marsupial of recent history, native to Australia, Tasmania and New Guinea. It was presumed extinct when the last known living specimen died in captivity in 1936.
Colossal intends to harness recent advances in DNA sequencing, genetic engineering and assisted reproductive technologies to de-extinct the animal and rewild it, restoring the Tasmanian and broader Australian ecosystems. According to Colossal, its conservation efforts are aimed at “combating the negative effects of the Anthropocene through ecosystem restoration as well as species preservation”.
What is the Anthropocene?
The Anthropocene Epoch is a term often used to describe the recent time period over which human activity has had a significant impact on the Earth’s ecosystems and climate.
For this de-extinction project, Colossal is collaborating with the University of Melbourne, specifically its Thylacine Integrated Genetic Restoration Research Lab (TIGRLab) led by Professor Andrew Pask. In 2018, Pask and colleagues published the first genome sequence of the Tasmanian tiger, data that is central to Colossal’s de-extinction project.
Technology Networks spoke with Lamm and Pask to further understand the aims of de-extinction, the logistics of the thylacine project and to discuss exo-pouches and artificial wombs.
Molly Campbell (MC): Colossal Biosciences states that it has started the de-extinction of the thylacine. For clarity, can you explain the stage at which the project is currently at?
Ben Lamm (BL): The process is very similar to the process the teams are leveraging for the de-extinction of the wooly mammoth. First samples of the extinct species must be collected, which Dr. Pask has achieved over the last decade. Next the sequencing of those samples and assembly of the thylacine genome must be completed and then compared to genomes of its closest living relatives – in this case, the dunnart, as well as other dasyurids.
The Colossal team of computational biologists then uses software to determine the right genes that need to be edited in the dunnart that will result in the phenotypes of the thylacine. Our genetics teams then leverage CRISPR and other gene editing tools to make the edits and leverage cloning technologies to transfer the edited nucleus to an egg, in order to create an embryo that can either be grown in a surrogate or an artificial womb. On the thylacine project, we are in the final analysis phase and will begin genetic engineering soon. Some edits have already started to take place and are being tested for efficacy.
MC: Why is the thylacine a particularly interesting creature for Colossal to focus its de-extinction efforts on? How does Colossal select extinct organisms for de-extinction?
BL: Colossal is committed to the de-extinction of keystone species, for which their return will result in a positive impact on the ecosystem they once thrived in, as well as developing key technologies that can also be used for species preservation. Of all the species proposed for de-extinction, the thylacine has arguably one of the most compelling cases. The thylacine was eradicated as a result of direct human influence less than 100 years ago, rather than through natural processes such as those that led to the extinction of the dinosaurs.
The thylacine was completely unique among living marsupials. Not only did it have its iconic wolf-like appearance, but it was also our only marsupial apex predator. Apex predators form extremely important parts of the food chain and are often responsible for stabilizing ecosystems. The habitat in Tasmania has remained relatively unchanged, providing the perfect environment to re-introduce the thylacine and enabling it to reoccupy its niche.
From a Colossal perspective, we are interested in pursuing de-extinction projects where the reintroduction of the restored species can fill an ecological void that was created when the species went extinct and help restore the degraded ecosystem. Now that the mammoth team is fully staffed and making great progress, we started to look for our second species to pursue. After being introduced to Dr. Pask and seeing his work on the Tasmanian tiger, as well as weighing the benefits for its de-extinction, we were excited to collaborate with him and University of Melbourne to help bring back a proxy for the thylacine.
Furthermore, we have incredible tissue samples and genomes assembled, as well as many additional pelts that are being sequenced for population genomics studies. Pask's work on the thylacine over the last decade makes him (and his lab) the best subject matter expert we could have ever hoped for on the project. Lastly, we are excited about how our work on the thylacine will lead to marsupial-focused conservation and gestational technologies that we weren't pursuing before starting on the project.
Andrew Pask (AP): The “tassie devil” facial virus is a classic example of what can happen when an ecosystem becomes unbalanced by the loss of an apex predator. The ripple of these impacts across the ecosystem are immeasurable, but the rewilding of the wolves into Yellowstone has shown us just how vital and complex some of these interactions can be. In the case of returning the wolf, not only did it impact the mammals in the system but also the vegetation right the way through to changing the course of rivers in the valley.
These animals hold pivotal positions in an ecosystem and when no other animal can replace that niche the effects are profound. In Tasmania it's only been 100 years or so since there was a population of thylacines in the ecosystem so we hope we can restore them before too much damage is done.
The Tasmanian tiger is the only marsupial apex predator that lived in modern times – so there are not any other native species that could replace it. It's very difficult to predict what a non-native predator might do to the ecosystem which is why species introductions into new habitats can lead to ecological disasters. The best thing we can do to protect our ecosystems is to prevent species extinctions. But where a corner-stone species has been lost from that environment, the next best thing we can do is try to bring that animal back.
MC: De-extinction does not mean that we literally re-create an extinct species, but rather a hybrid version. For our readers that may be unfamiliar, can you explain how this process works?
AP: De-extinction is distinct from cloning in that we don’t have a living cell (from our extinct animal) to start the process. In this case we have to look for the closest living relative to serve as a host for bringing back our extinct species. In the case of the thylacine, this is the fat tailed dunnart – a mouse-sized carnivorous marsupial. We then sequence the genomes of our extinct animal and the closest relative and compare them. Next, we take living cells from our dunnart and edit their DNA every place where it differs from the thylacine. We are essentially engineering our dunnart cell to become a Tasmanian tiger cell.
Then we use standard stem cell and reproductive techniques to turn that cell back into a living animal. Our ultimate goal with this technology is to restore these species to the wild where they played absolutely essential roles in the ecosystem. We hope that you will see them in the Tasmanian bushland again one day.
BL: Our goals are to get as close as possible to the original extinct species in terms of its size, shape and behaviour. I have seen some people argue the word "de-extinction" over the last few years and, in my opinion, people should be less concerned with the semantics of the word and more concerned with developing tools to rapidly advance conservation and save species. The technologies we are developing have massive applications to conservation. We are also bringing back genes and phenotypes that were extinct. If you create a proxy species that has all the phenotypic traits you are looking for, how is that not de-extinction if the resulting proxy animal fills the ecological void that was created with its absence?”
MC: Can you talk about the current marsupial assistive reproductive technology and the advancements required? How will these be used to help preserve other marsupials?
BL: In addition to the benefits of rewilding and helping to balance an ecosystem that mankind had a hand in its degradation, Colossal is developing marsupial-focused conservation and gestational technologies that will support broader marsupial conservation efforts. For example, we are developing an exo-pouch that the joeys will further develop in post-birth.
The exo-pouches can be utilized for existing marsupial species, such as the Tasmanian devil. The Tasmanian devil gives birth to between 20–30 joeys. However, the mother has only four nipples, so only a handful of babies survive. Our exo-pouch could be incredibly helpful to conservationists working with the Tasmanian devils to take those additional 20+ joeys and give them a place to incubate further.
In addition, Colossal is working on full-stage artificial wombs that can help in full ex-utero development all the way from embryos. These gestational technologies alone will be transformational for marsupial conservation.
MC: Can you talk about the re-wilding process planned for the thylacine and how it will ensure that history does not repeat itself?
AP: Humans are rapidly changing the environment. Global temperatures are rising, adverse weather events (such as the devastating bushfire in Australia in the past few years) are predicted to increase in frequency and severity and we are introducing pest species all over the planet. Unless we step in to help these species, we will lose vast amounts of biodiversity.
The technologies we are developing to de-extinct the thylacine all have immediate conservation benefits – right now – to protect marsupial species. Biobanks of frozen tissue from living marsupial populations have been collected to protect against extinction from fires. However, we still lack the technology to take that tissue – create marsupial stem cells – and then turn those cells into a living animal. That is the technology we will develop as a part of this project. Even the genome editing can help protect marsupials against invasive pest species or increase genetic diversity and population health.
BL: The thylacine extinction is a tragic story. It was an incredible animal that was not like anything else. It was falsely accused of eating sheep which led to the Australian government putting a bounty on the species. It was hunted to extinction at the hand of mankind. Much of its habitat is still intact. The ecosystem it will be rewilded to is still missing an apex predator and needs this ecological niche filled. We are confident that with proper protection and no hunting bounties, the thylacine will thrive again in the wild.
MC: Can you talk about the ethical approvals required for de-extinction projects? Do these vary depending on the species/ region?
AP: In the case of the thylacine, the benefits of returning this species would far outweigh any potential risks. Any release such as this requires studying the animal and its interaction in the ecosystem over many seasons and in large areas of enclosed land before you would consider a complete rewilding. The impacts of the loss of the thylacine can already be seen with the rapid spread of new diseases like the Tasmanian devil facial tumor disease which almost led to the extinction of another marsupial species. We would strongly advocate that first and foremost, we need to protect our biodiversity from further extinctions, but unfortunately, we are not seeing a slowing down in species loss. This technology offers a chance to correct this and could be applied in exceptional circumstances where cornerstone species have been lost – to help prevent further damage to the ecosystem.
MC: What are the expected timelines for this project?
BL: We have been vocal about our ambitious goals to get our first mammoth calves in the next five to six years. While we aren't announcing a timeline yet for the thylacine, the gestational time for marsupials is measured in weeks compared to 22 months with elephants. A large part of our mammoth timeline is based on the nearly two-year gestation of the calves. I think it is safe to assume that the thylacine proxy could be one of the first animals to be brought back.
MC: What challenges do you expect to encounter in this de-extinction project, and how will you look to overcome them?
AP: We have all the technology in hand for other species, but a lot of these techniques have not yet been applied to marsupials. We will need to develop marsupial stem cells (which we think we have achieved already) and then reproductive technologies to turn those cells back in living animals. All these challenges just need a lot of science-hours to solve and this new partnership with colossal brings an incredible team together to solve some of these problems!
Ben Lamm and Professor Andrew Pask were speaking to Molly Campbell, Senior Science Writer for Technology Networks.
