Some extinction is natural. Changes to ecosystems and poor reproductive tendencies can cause a species’ mortality rate to exceed its birth rate until none remain. Humans hunt, overharvest, introduce invasive species, pollute, and convert wetlands and forests to croplands and cities, causing other species to become extinct. Even fast population expansion is destroying natural areas, triggering extinction.
The big idea
In 1990, Michael Crichton released his science fiction novel Jurassic Park. In this book, he envisaged a future in which scientists were able to bring extinct animals back to life. This work marked the beginning of the tale as it is told in the present era. Because Crichton had received his education in biomedical science, he was familiar with the innovative polymerase chain reaction (PCR) technology that was reshaping laboratories that dealt with life sciences at the time.
Molecular scientists were able to create millions or billions of copies of DNA extremely fast thanks to a technique called PCR. This meant that only very few samples were required.
Back-breeding vs. CRISPR
In the 20th century, back-breeding was used to resurrect extinct animals by using selective breeding to reintroduce ancestral traits that had been lost through evolution.
Cloning was the first ‘successful’ de-extinction method, however back-breeding is still practiced. The last live bucardo, Celia, died in 2000. In 2003, scientists cloned her using a method developed from Dolly the Sheep, the first mammal cloned from an adult somatic cell.
The newest option being researched for de-extinction is Clustered Regularly Interspaced Short Palindromic Repeats CRISPR, a gene-editing tool that is still relatively young. The Cas9 protein cuts an RNA guide tailored to target certain genomic regions in CRISPR. It allows scientists to modify DNA by adding or removing genetic information.
CRISPR for de-extinction begins with genome sequencing to create a blueprint for the extinct species. The order of the four bases in the DNA molecule will be determined by genome sequencing. This requires scientists to get the genome of its nearest living cousin.
Researchers compare the genomes of the extinct species and its living relatives and introduce key elements of the ancient animal’s DNA into the live relative’s genome. Mammoth cold-resistance must be incorporated into the Asian Elephant DNA.
As promising as the technology is, CRISPR for de-extinction cannot entirely recreate an extinct species. The fact is that gene editing technology is not mature enough to quickly create an exact clone. Changing all extinct animal DNA sequences would take hundreds of years.
Reintroduce the Dodo back
Colossal Biosciences, the headline-grabbing, venture-capital-funded behemoth of de-extinction science, has announced plans to revive the dodo.
Most de-extinction initiatives use genetic engineering to simulate an extinct animal’s genome by modifying a closely comparable current species’ genome. The altered genome would be placed into a similar species’ egg cell to develop. The method must assure proper growth, successful birth, competent surrogate parents, nutritious food, and an ideal atmosphere.
The first stage of altering the genome of animals is more difficult; the subsequent stages should be simpler. In the case of mammals, scientists do not yet know how an extinct species’ modified embryo will interact with the intrauterine environment of the host species. In birds, this stage will be simplified because everything occurs in the egg.
Even if it becomes possible to create an avian with a dodo genome, it is impossible to bring back the dodo. Beyond behavior, the dodo proxy must survive in a world that has changed substantially since the dodo went extinct over 300 years ago.
Ethical solutions
De-extinction can be perceived as a solution to biodiversity loss and a progressive conservation tool, or as a distraction from present conservation efforts and a threat to ecosystems.
The recent push for de-extinction is driven by the desire to bring back animals that were driven to extinction by humans rather than natural, evolutionary causes. In principle, reintroducing extinct animals to their original environment will boost biodiversity.
Most current extinctions are caused by human activity, a trend that is growing. In October 2022,a research found that rainforest destruction, pollution, overfishing, and trophy hunting have reduced animal numbers by 69% since 1970.
De-extinction raises ethical concerns, as some scientists and conservationists argue that the species’ brought back to life habitat will no longer exist, and they may not be able to survive in the wild, ending up in cages and zoos. Another issue is whether reintroduction into the wild may disrupt ecosystems and food networks.
There is no precedence for bringing an extinct species back to life long enough to see how it affects the environment, so it’s hard to predict if de-extinction will be beneficial or harmful.
