The idea of bringing extinct animals back to life has long captivated the public imagination, often fueled by dramatic portrayals in popular culture. This fascination frequently turns to creatures like dinosaurs. Beyond fiction, scientists are actively exploring de-extinction, a process aiming to regenerate organisms resembling or identical to those that have vanished. This scientific endeavor involves advanced genetic techniques and is grounded in the potential to restore lost biodiversity.
The Science of De-Extinction
De-extinction research employs several scientific approaches to recreate extinct species. One primary method is cloning, specifically using somatic cell nuclear transfer (SCNT). This process involves taking the nucleus from a preserved cell of the extinct species and inserting it into an egg cell from a closely related living species, after the egg’s original nucleus has been removed. The reconstructed egg is then stimulated to develop into an embryo, which is implanted into a surrogate mother of the living relative.
Another technique involves genetic engineering, often utilizing CRISPR gene editing. This allows scientists to introduce specific genes from an extinct species into a living relative’s genome, effectively editing the DNA to express traits of the vanished animal. This approach can create a hybrid that possesses characteristics of the extinct species. Selective breeding, or back-breeding, is a more traditional approach that aims to replicate ancestral traits by crossbreeding living descendants. This method can result in animals that visually and behaviorally resemble their extinct ancestors.
The Dinosaur De-Extinction Question
Despite popular culture narratives, bringing dinosaurs back from extinction is not scientifically feasible. The primary obstacle is the extreme degradation of dinosaur DNA over millions of years. DNA is a fragile molecule that breaks down quickly after an organism dies. Fossilization replaces organic material with minerals, meaning dinosaur bones typically do not contain viable DNA.
The oldest DNA ever recovered is around 1 to 1.5 million years old, preserved in conditions like permafrost. Dinosaurs became extinct approximately 65 million years ago, making intact, usable DNA recovery impossible with current technology. Even if fragments were found, they would be too damaged and incomplete to reconstruct an entire genome.
Extinct Animals Under Consideration for Revival
While dinosaurs remain beyond current de-extinction capabilities, scientists are actively working on or considering the revival of several more recently extinct species.
Woolly Mammoth
The woolly mammoth is a prominent candidate, with projects like Colossal Biosciences aiming to bring back a cold-resistant elephant resembling the mammoth. This involves editing the genome of the Asian elephant, the mammoth’s closest living relative, which shares 99.6% of its DNA. The goal is to reintroduce these animals to the Arctic to potentially restore ancient grasslands and combat permafrost thaw.
Passenger Pigeon
The passenger pigeon, once North America’s most abundant bird, is another species targeted for de-extinction by organizations like Revive & Restore. Its relatively recent extinction in the early 20th century means better-preserved DNA is available. Scientists plan to use gene-editing to introduce passenger pigeon traits into its closest living relative, the band-tailed pigeon.
Thylacine (Tasmanian Tiger)
The thylacine, also known as the Tasmanian tiger, is a focus for Colossal Biosciences due to its extinction in 1936. Researchers are working to engineer cells from the fat-tailed dunnart, a close marsupial relative, to create thylacine-like cells using gene editing.
Pyrenean Ibex
A notable de-extinction case occurred in 2003 with the Pyrenean ibex, a wild goat subspecies. Using cloning techniques, a living Pyrenean ibex was born from preserved tissue of the last individual. Though the cloned animal survived for only minutes due to a lung defect, its birth marked the first time an extinct animal had been brought back, even briefly.
The Path to Revival: Scientific Hurdles
Bringing an extinct species back to life involves significant scientific and biological obstacles.
Surrogate Mothers and Success Rates
One major hurdle is securing suitable surrogate mothers for gestation. For large mammals like the woolly mammoth, using an endangered Asian elephant as a surrogate presents challenges, including potential miscarriages and ethical implications. The process of cloning often has very low success rates, as demonstrated by the Pyrenean ibex project where only one clone was born from hundreds of attempts.
Genetic Reconstruction and Diversity
Even with viable DNA, reconstructing a complete and functional genome remains complex. Gene editing often results in a hybrid animal rather than an exact replica, and missing genetic information can lead to unforeseen biological issues. Ensuring sufficient genetic diversity within a revived population is difficult when starting from limited genetic material, which can lead to inbreeding and reduced adaptability.
Ecosystem Reintegration
Reintroducing a revived species into an ecosystem that has changed dramatically since its extinction presents further challenges. The original habitat may no longer exist, food sources might be different, and predator-prey relationships could be altered. Scientists must consider how a reintroduced species would impact existing flora and fauna, and whether it could successfully establish a self-sustaining population.