Reviving the Past: Can We Bring Back Extinct Species?
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Using DNA to revive lost species and traits is becoming a feasible idea, but is it ethically sound?
The term "extinction" implies irreversible disappearance—an end to existence. However, advancements in DNA sequencing challenge this notion. Just how lost are these species?
Consider the likes of dinosaurs, passenger pigeons, woolly mammoths, and the mountain hibiscus of Hawai’i, alongside numerous others cataloged on Wikipedia.
Recently, I encountered an article by Rowan Jacobsen in Scientific American, detailing how scientists retrieved genes from ancient herbarium specimens to recreate plant scents that had not been experienced in over a century. This sparked my interest.
In my pursuit of knowledge, I explored the literature and online resources, uncovering that while the idea of resurrecting these species is alluring, it is fraught with complexities.
Challenges include scientific hurdles, ethical questions, ecological impacts, and financial considerations.
Take, for example, the passenger pigeon. If we manage to overcome the scientific challenges and successfully recreate them, is it justified? What about their survival? Would they adapt to today’s environment?
Furthermore, what implications would their return have on existing species that have filled the ecological void left by their absence? Could they potentially become invasive?
If the endeavor costs a million dollars for just ten passenger pigeons, would that investment be better allocated to other research?
Clearly, the matter is intricate.
Let's explore the realm of de-extinction and better understand the accompanying challenges and ramifications.
First, let's discuss the scientific principles at play.
De-Extinction and Resurrection Science
Globally, scientists are engaging in efforts to revive species that have been lost to time, a field often referred to as species revivalism.
Currently, three prominent methods dominate this research: cloning, gene editing, and selective breeding.
Cloning
Most people are familiar with the concept of animal cloning, exemplified by Dolly, the first cloned mammal. Since then, cloning has been applied to dogs, pigs, and horses as well.
Cloning involves taking a nucleus from a preserved somatic cell and inserting it into an egg cell whose nucleus has been removed.
The egg is then placed in a surrogate host, and if successful, it develops into the desired animal.
For instance, in 2003, scientists aimed to resurrect the Pyrenean ibex using tissue from the last known female of the species, Celia. A goat’s egg was used, and the resulting embryo was implanted into a surrogate goat.
However, significant obstacles remain. The first is obtaining a well-preserved cell capable of providing an intact nucleus. The most successful attempts are likely to come from species that recently went extinct, as their cells are less degraded.
Celia, the final Pyrenean ibex, had tissue samples collected in 1999. After her death in 2000, cloning attempts in 2003 resulted in only one successful pregnancy, which ended tragically shortly after birth due to a lung defect.
Another challenge is immune rejection. Just as organ transplants can fail due to a recipient's immune system, so too can cloning efforts. Given that Celia was the last of her kind, knowledge of her immune system is limited.
There are also ethical considerations regarding cloning, as it creates genetically modified organisms, which many oppose.
Gene Editing
Gene editing offers a different approach, as it doesn’t require highly preserved cells. If sufficient DNA can be extracted from an extinct organism, sequencing can provide a fair reconstruction of its genome.
This allows scientists to modify the DNA of a closely related species to more closely resemble that of the extinct organism.
Returning to the Pyrenean ibex example, if a closely related ibex species is available and we know the Pyrenean genome, gene editing could allow the creation of embryos with altered DNA resembling the extinct species.
Selective Breeding
Selective breeding, particularly back-breeding, focuses on breeding current related species to bring back ancient traits over many generations.
For this to succeed, the genes for those traits must still exist within the population of a related species and be functional.
Imagine modern elephants with genes for hairiness, reminiscent of woolly mammoths. By selectively breeding these elephants, we might produce individuals that visually resemble woolly mammoths, but they would still be fundamentally modern elephants.
A more advanced method combines gene editing with cloning to create hybrids of extinct and extant species.
Consider the woolly mammoth, a species that Harvard's George Church is attempting to revive. His strategy involves using DNA from a well-preserved young female mammoth and integrating it into an Asian elephant's genome using CRISPR technology, with the goal of creating a hybrid.
This overview highlights the scientific techniques currently utilized in the quest to revive extinct species.
De-extinction Ethical Considerations
Focusing on the tangible pros and cons of de-extinction, one argument for revival is the moral obligation to restore species driven to extinction by human activities.
Examples of human-caused extinction include habitat destruction, overhunting, and climate change.
The case of the hau kuahiwi, a mountain hibiscus that vanished due to environmental changes caused by colonial ranching on Maui, exemplifies this. The last known tree died around 1912, its seeds consumed by invasive species, leading to its extinction.
Researchers managed to collect its last flower for preservation, which has led to DNA recovery and sequencing.
However, if resurrected, would the plant thrive in a changed landscape? Would humans need to intervene continuously to ensure its survival?
Can we realistically expect land used for economic purposes to revert to its natural state for the sake of an extinct plant?
Or, if an animal were successfully revived, could it potentially disrupt existing ecosystems, becoming an invasive species?
These questions are complex and multifaceted.
What About the Passenger Pigeon and Woolly Mammoth?
Both of these species are viewed as viable candidates for revival.
Dr. Church believes restoring the woolly mammoth could help mitigate climate change effects and rejuvenate the arctic tundra. The plan involves using mammoths to graze on vegetation that currently insulates the tundra, allowing the ground to freeze and restoring the ecosystem.
As for the passenger pigeon, once numbering in the billions, their extinction was driven by overhunting and habitat destruction.
Ben Novak aims to revive them using DNA from museum specimens and related species, employing cloning techniques to create genetically diverse offspring.
Yet, challenges remain. The forests they depended on have largely disappeared, and their natural food sources may be scarce.
Despite these hurdles, Novak and his team remain optimistic about the potential for success.
What’s Happening with the Hau Kuahiwi Mountain Hibiscus?
Currently, no efforts are underway to restore the hau kuahiwi plant itself. Instead, scientists are focusing on recovering specific scent-related genes.
Ginkgo Bioworks is interested in reviving the plant's fragrance for the fragrance industry. They obtained a small piece of the herbarium specimen for DNA extraction and sequencing.
After identifying potential scent genes, they synthesized these genes and introduced them into specially engineered yeast strains.
The resulting scents ranged from citrus to woody aromas, encapsulating the essence of the extinct plant.
This marks a significant achievement in the recovery of lost scents and could pave the way for future projects.
Ultimately, even if we do not fully resurrect organisms, recovering essential genes and traits remains promising for potential future benefits.
I look forward to witnessing the advancements in de-extinction efforts!
Until next time, happy exploring!
Rich
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P.S. I managed to discuss de-extinction without referencing Jurassic Park—a noteworthy achievement!
Sources for this article: 1. Fragrant Genes of Extinct Flowers Have Been Brought Back to Life by Rowan Jacobsen. 2. 100 years ago, the very last passenger pigeon died by Joseph Stromberg. 3. The Revival of the Passenger Pigeon? by Sarah Pruitt. 4. Scent of Extinct Maui Mountain Hibiscus Revived by Science by Wendy Osher. 5. Woolly mammoths could come back to life and SAVE the Arctic by Phoebe Weston. 6. List of animals that have been cloned, Wikipedia. 7. Passenger Pigeon, Wikipedia. 8. De-extinction, Wikipedia. 9. Pathways to de-extinction: how close can we get to resurrection of an extinct species? by Beth Shapiro. 10. Ancient DNA Calling Out for “De-Extinction” — How far can or should we go? by F. Javier Carmona.