Bring Back the Dinosaurs: The Use of CRISPR-Cas9 for De-Extinction
According to the National Museum of Natural History, there are around 8 million documented species of living organisms, 15,000 of which are currently threatened by extinction. These figures do not include the countless species already extinct, such as dodo birds, golden toads, and as of 2004, St. Helena olive trees (Extinction Over). With the rise of overhunting, climate change, deforestation, and industrialization, many scientists argue that a 6th mass extinction is taking place, jeopardizing the future of numerous animals and plants. This reality has spurred a collective response amongst environmentalists, resulting in a unique method to counter species loss: de-extinction.
De-extinction began to gain popularity in 2013, following the TEDxDeExtinction event, held by the National Geographic Society and Revive & Restore, a conservationist nonprofit organization (Novak 1). This event led to the announcement of the project, “The Great Passenger Pigeon Comeback,” an infamous de-extinction project to bring back the passenger pigeon. The support and momentum generated in the following 3 years would lead to the development of specific guidelines for de-extinction in 2016. Set by the International Union of the Conservation of Nature (IUCN), the IUCN SSC Guiding Principles on Creating Proxies of Extinct Species for Conservation Benefits would define de-extinction as “the process of creating an organism that resembles an extinct species,” noting that this process is used to create a proxy of a once-existing species or subspecies (IUCN SSC Guiding 1). These guidelines outline 3 methods for the creation of proxy organisms, back-breeding, cloning, and genome editing. Once clearly defined, the field of de-extinction would prosper, with countless scientists, researchers and environmentalists promoting genetic innovation.
The first possible de-extinction method is back-breeding, the historical predecessor to cloning and genome editing. Formally defined, back-breeding uses “selective breeding to bring back ancestral traits” of extinct species (Odenbaugh 2). Currently, Grazelands Rewilding is attempting to use back-breeding to de-extinct the auroch, the ancestor of modern cattle. The auroch became extinct in 1627 due to overhunting, severely impacting the ecosystems of European nations (Born to Be Wild). However, back-breeding can only result in a species that resembles the auroch, with similar physical attributes and grazing habits. The created species will not be genetically identical, meaning this process could inevitably result in higher rates of genetic mutation or inbreeding if successful. This makes it less ideal in the context of de-extinction.
The next possible de-extinction method is cloning. Cloning uses somatic cell nuclear transfer (SCNT) to create an identical genetic sequence to the donor of the cell, allowing for a genetically identical form of the animal. On July 5, 1996, the first cloned creature was created. Dolly the Sheep, developed by researchers at the Roslin Institute of the University of Edinburgh, was born (Rozenbaum). While revolutionary, this process does face one key-drawback: the need for living cells of the creature that is being cloned. As such, it is difficult for the de-extinction of historical creatures, whose living cells could be collected or maintained.
This led to the most recent and promising process for de-extinction, genetic editing. Genetic editing was first introduced in the 1990s, resulting in immense fervor within the scientific community. Relying on the manipulation of a living organism’s material, genes can be introduced, deleted or manipulated. By doing so, an existing species can be completely changed or altered to resemble and replicate one that once existed. As the process developed, it began to rely on one specific form of technology: CRISPR-Cas9. CRISPR-Cas9, short for clustered regularly interspaced short palindromic repeats (CRISPR), is an “engineered cellular technology that has an RNA guide that is programmed to target specific areas on a genome, with Cas9 protein acting as scissors” (Shah-Neville). First, scientists sequence the extinct animal’s genome, determining the order of the primary chemical building blocks (A, G, T, and C) in its DNA. Then, parts of the extinct species genome is inserted to a living, related creature. The parts of the genetic sequence inserted are generally critical traits that are missing between the extinct species and the one that evolved from it, meaning they are necessary tocompletely “recreate” the species. Finally, a CRISPR-Cas9 complex that contains RNA is used to bind the added traits, allowing for the creation of a hybrid version of the extinct animal.
Several modern efforts have utilized this technology to pursue de-extinction. One such example is the Wooly Mammoth. The long-lost face of the Pleistocene Ice-Age, Wooly Mammoths were herbivorous roamers characterized by thick brown hair and large, bulky tusks. Their presence throughout North America, Asia, and Europe greatly impacted the arctic ecosystem until their extinction around 10,000 years ago (Wooly Mammoth). Scientists believe that the de-extinction of the Wooly Mammoth could restore arctic landscapes increasingly impacted by climate change. As such, Colossal Biosciences is investing in the project, attempting to use CRISPR-Cas9 technology to edit the genetic sequence of Asian Elephants, a close ancestor to the Wooly Mammoth. The primary goal of scientists is to reconstruct the elephant's DNA to adapt to extremely cold climates, a critical feature of the Mammoth lost by ancestors after their extinction (Chen 18). As such, this ongoing project demonstrates the current impact of CRISPR-Cas9 on the field of de-extinction.
As scientific research centers around de-extinction, the environmental implications of the process must be considered. Firstly, it is unsure how the introduction of “edited” species, those that have been genetically altered to resemble the traits of extinct species, will impact the natural ecosystem. Caplan et al. explain that scientists are already demanding strict regulations for the release of altered species into the environment (Caplan et al. 1422). However, considering de-extinction via genetic modification is a relatively new process and far from successful or widespread, little has been done. Secondly, several species could be decimated as they begin breeding with mutated creatures, as the traits of the existing species are slowly replaced with mutated genes. Finally, it is unknown if these lab-bred creatures will be able to flourish in the natural environment. Few animal adaptations have been successful, meaning scientists have little evidence that CRISPR-Cas9 can effectively create long-lasting animals.
Another implication of any genetic editing, especially one involving de-extinction, is the ethical dilemma. One of the widespread objections to the practice is that it can cause unnecessary harm to living creatures. CRISPR-Cas9 technology is far from perfect, resulting in complications like miscarriage, early birth, genetic abnormalities, and early death (Odenbaugh 4). Therefore, is it worth inflicting potential harm on animals in the process of “remaking” extinct species? Another argument is that geneticists are currently “playing God” by attempting to resurrect species of the past. Should the scientific community have the ability to alter past human mistakes and if so, at what point should this be prevented? Even scientists in support of the process espouse concerns about the minimal regulations, as it becomes easier to cross ethical boundaries when lacking supervision and legal repercussions.
Ultimately, de-extinction is becoming increasingly popular across the globe as labs attempt to “resurrect” iconic animals from the past. From Dodo Birds to Wooly Mammoths, the long lost species of the past are not as extinct as previously thought. However, this immense scientific innovation is not without risk, as ethical and environmental implications plague scientists. Regardless, this new and exciting technology is on the forefront of genetic engineering. It is unknown how it will continue to develop in the next 5 years. However, be certain that the field will continue to change as innovation prospers. Extinction is potentially reversible, a groundbreaking development only made possible with the advent of CRISPR-Cas9 technology.
References
"Born to Be Wild." Rewilding Europe, rewildingeurope.com/rewilding-in-action/wildlife-comeback/tauros/#:~:text=The%20principal%20technique%20is%20%E2%80%9Cback,of%20Europe's%20original%20wild%20aurochs. Accessed 29 Mar. 2025.
Caplan, Arthur L., et al. "No Time to Waste—The Ethical Challenges Created by CRISPR." EMBO Reports, vol. 16, no. 11, 8 Oct. 2015, pp. 1421-26, https://doi.org/10.15252/embr.201541337. Accessed 30 Mar. 2025.
Chen, Yue Ning. "The Potential of CRISPR-Cas9 Genome Editing on the Woolly Mammoth Revival." Young Anthropology, vol. 5, fall 2024, pp. 15-22, file:///C:/Users/Josh%20Stubbins/Downloads/3.YA5_Chen_article_formatted_final_Oct31.pdf. Accessed 30 Mar. 2025.
Extinction Over Time." National Museum of Natural History, Smithsonian, naturalhistory.si.edu/education/teaching-resources/paleontology/extinction-over-time. Accessed 16 Mar. 2025.
"IUCN SSC Guiding Principles on Creating Proxies of Extinct Species for Conservation Benefit." International Union of the Conservation of Nature, 2016, portals.iucn.org/library/sites/library/files/documents/Rep-2016-009.pdf. Accessed 16 Mar. 2025.
Novak, Ben Jacob. "De-Extinction." Genes, vol. 9, no. 11, 13 Nov. 2018, https://doi.org/10.3390/genes9110548. Accessed 16 Mar. 2025.
Odenbaugh, Jay. "Philosophy and Ethics of De-Extinction." Cambridge Prisms, vol. 1, 30 Jan. 2023, https://doi.org/10.1017/ext.2023.4. Accessed 29 Mar. 2025.