The dodo, an iconic flightless bird, has long symbolized human-driven extinction. In an era of rapidly advancing biotechnology, the question of its return is gaining scientific attention. Researchers are exploring de-extinction, a field that seeks to bring back vanished species. This article examines the scientific methods, current initiatives, and challenges involved in potentially resurrecting the dodo.
The Dodo’s Extinction
The dodo (Raphus cucullatus) was a large, flightless bird endemic to the island of Mauritius. These birds stood about 62.6 to 75 centimeters tall and could weigh between 10.6 and 17.5 kilograms. Its unique appearance was a result of evolving in an environment with abundant food and no natural predators. This lack of predators meant the dodo had no reason to fly.
The arrival of Dutch sailors on Mauritius in 1598 marked the beginning of the dodo’s rapid decline. While direct hunting contributed, the primary drivers of extinction were invasive species introduced to the island. Rats, pigs, cats, and monkeys preyed on dodo eggs and young, which were vulnerable as the birds nested on the ground and typically laid only a single egg per clutch. Habitat destruction through deforestation further reduced their food sources and living space. The species was likely extinct by 1690, making it a prominent example of human-caused extinction.
The Science of De-Extinction
De-extinction, also known as resurrection biology, aims to generate organisms that resemble or are closely related to extinct species. This endeavor leverages advanced genetic and reproductive technologies. One method is cloning, which involves transferring the nucleus from a preserved cell of the extinct species into an enucleated egg cell from a closely related living species. However, cloning requires intact living cells, making it challenging for long-extinct species like the dodo, for which no living cells exist.
Another, more promising approach for species extinct for centuries is genome editing, particularly using tools like CRISPR. This technique involves modifying the DNA of a living relative to incorporate genes from the extinct species. CRISPR acts as molecular scissors, allowing scientists to cut and insert specific genetic information into the target genome. The goal is to create a hybrid by editing the genome of the closest living relative to express traits characteristic of the extinct animal.
This process begins with sequencing the extinct species’ genome from ancient DNA samples, which can be fragmented and degraded, posing a significant hurdle. The resulting organism is not an exact genetic replica but a hybrid that possesses many of the desired traits of the extinct species.
Current Efforts to Revive the Dodo
In February 2023, the biotechnology company Colossal Biosciences announced its initiative to de-extinct the dodo. This project builds upon the company’s work with other extinct species. Their strategy centers on using gene editing to modify the genome of the Nicobar pigeon (Caloenas nicobarica), considered the dodo’s closest living relative.
The process involves several complex steps. First, scientists sequence the dodo’s genome from preserved specimens, a task completed in 2021. This genetic blueprint guides the identification of specific dodo traits for introduction into the Nicobar pigeon’s DNA. The challenge lies in editing the Nicobar pigeon’s germ cells to carry these dodo traits, potentially through primordial germ cells (PGCs).
The aim is to develop chimeric chicks that carry the dodo’s genetic characteristics. This approach seeks to create an animal functionally similar to the dodo, with the long-term goal of reintroducing these hybrids into their native Mauritian environment.
Ethical and Practical Hurdles
Bringing back an extinct species like the dodo presents numerous scientific and practical challenges. A primary hurdle is the quality of ancient DNA; the dodo’s DNA is fragmented, making complete genome reconstruction difficult. Even with advanced gene editing, perfecting the technique to accurately replicate all traits remains a significant scientific endeavor. Reproductive challenges with surrogate species are considerable, particularly for birds, as avian reproduction differs from mammals.
Beyond the scientific intricacies, ecological considerations pose substantial questions. Reintroducing a de-extinct dodo would require a suitable habitat, but Mauritius’s ecosystem has changed drastically since the dodo’s disappearance. The original forests are largely gone, and the island is now home to numerous introduced species.
There is concern that introducing a “new” species could disrupt the existing ecosystem, potentially impacting native species or introducing diseases. Ethical concerns also surround de-extinction efforts. Questions arise regarding the welfare of surrogate animals and the potential for revived animals to adapt to a vastly altered environment.
Critics also debate resource allocation, suggesting funds and expertise could be more effectively used for conserving endangered species and their habitats. Legal frameworks for de-extinct species are nascent, addressing ownership, conservation status, and environmental impacts. These challenges highlight that the potential return of the dodo involves complex considerations beyond scientific capability.