All good things in life must come to an end. Sometimes it is expected, like an organism reaching the end of its life, and sometimes it is less predictable; like the meteor that hit the dinosaurs. Extinction is a natural part of Earth’s history, and over billions of years, countless species have disappeared from the planet entirely (Jebari and Sandberg 2022). Once a species goes extinct, most generally consider it gone for good. But what if extinction didn’t have to be the final chapter? With recent advances in genomics and gene-editing technology, scientists are exploring whether some extinct species could one day be brought back to life (Lin et al. 2022).
But.. how on Earth could scientists bring back something that has been extinct for thousands, or even millions of years? Well, the key lies in the genetic information that was preserved within the remains of extinct species. Scientists can extract fragments of ancient DNA from these remains and sequence them to reconstruct as much of the extinct species’ genome as possible (Lin et al. 2022). This genome can then be compared with that of a closely related living species, allowing researchers to identify genetic differences that may be associated with traits characteristic of the extinct species. Researchers can then modify these specific regions in cells of the living species using gene-editing technologies such as CRISPR-Cas9 to potentially produce an organism with selected traits of its extinct relative (Turner et al. 2026).
A 2022 study tested the feasibility of this approach by using the extinct Christmas Island rat (Rattus macleari) as an example. In the study, researchers re-sequenced DNA from ancient preserved remains and found that, even with high-quality sequencing with large amounts of coverage, 4.85% of the Christmas Island rat’s genome could not be recovered when compared with the closely related Norway brown rat. Furthermore, the missing regions were not random; genes involved in immune function and smell were particularly affected. This suggests that even a genetically engineered version of an extinct species is not an identical replication, and could differ from the original in many different ways (Lin et al. 2022).
De-extinction could also have consequences larger than just the individual organism. Changes in genes involved in important traits could affect how a recreated organism interacts with its environment, other species or with potential diseases. It is therefore also important to consider how these organisms could function within modern ecosystems, and whether their reintroduction could have effects that scientists cannot currently predict (Wienhues et al. 2023)
Extinction may no longer be as definite as it once seemed, but bringing an extinct species back is far more complicated than simply recovering its DNA. As technology continues to advance, scientists may become more capable of replicating a species’ genome, but a genome alone cannot perfectly recreate everything that made a species what it was. De-extinction therefore raises the question: if a species cannot be perfectly replicated to what it once was, have we truly reversed its extinction?
References
Jebari, Karim, and Anders Sandberg. 2022. “Ecocentrism and Biosphere Life Extension.” Science and Engineering Ethics 28 (6): 46. https://doi.org/10.1007/s11948-022-00404-2.
Lin, Jianqing, et al. 2022. “Probing the Genomic Limits of De-Extinction in the Christmas Island Rat.” Current Biology 32 (7): 1650–1656.e3. https://doi.org/10.1016/j.cub.2022.02.027.
Turner, Stephen D., et al. 2026. “De-extinction Technology and Its Application to Conservation.” Journal of Heredity 117 (5): 959–974. https://doi.org/10.1093/jhered/esaf069.
Wienhues, Anna, Patrik Baard, Alfonso Donoso, and Markku Oksanen. 2023. “The Ethics of Species Extinctions.” Environmental Values 1: e23. https://doi.org/10.1017/ext.2023.21.
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