Bringing extinct species back to life is no longer science fiction, even if the technology isn't quite ready for it. Much of the hype on this topic has been raised by the renewed constant attempts to return woolly mammoths to earth. And not only. Not so long ago, Harvard geneticist George Church announced that his team would be able to present a hybrid embryo in two years. An Asian elephant will be genetically created, and some mammoth traits will be transferred to this new species.
The idea to return to our planet those that have become extinct through our and not only our fault is far from new. The first attempt to reclaim a lost species, the wild ibex bucardo, was made in 2003, three years after the species went extinct. The cloned Bucardo (Pyrenean ibex) embryo was raised in a laboratory and then inserted into the womb of a goat to be carried. He managed to live only a few minutes due to a lung defect.
Attempts to revive the woolly mammoth - or a genetically modified version of it - have been even more frequent.
Japanese scientists have tried to clone the woolly mammoth for over 15 years. They still have not been able to do this. Scientists like Church believe it is necessary to create a hybrid, not a perfect clone, using a gene editing technique called CRISPR / Cas9.
The right tool for the job
CRISPR / Cas9 allows you to edit the genome of any living organism. It gained notoriety in 2012 and was touted as a possible treatment for cancer and a number of genetic diseases, among other amazing uses. This technique was based on the mechanism of protecting bacteria from viruses.
In fact, a gene editing tool allows scientists to rewrite the "history" of an organism's genetic makeup. Its simplicity and precision in cutting and gluing genetic material makes it extremely versatile, allowing small pieces of DNA to be replaced.
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Since 2015, Church-led scientists have made 45 "fixes" to the Asian elephant genome. For the most part, they were interested in the characteristics of the woolly mammoth - such as subcutaneous fat and long hair - that made them particularly well adapted to the cold before they finally died out about 4,000 years ago.
The right genetic material is needed
It turned out that not all woolly mammoth DNA is suitable for the resurrection of the species. A study published this month in PLOS Genetics says that shortly before extinction, one of the last groups of woolly mammoths experienced a "genetic crisis" that resulted in many nasty genetic mutations in its genome.
The study compared the genome of a continental woolly mammoth, which lived 45,000 years ago, when there were many animals, with the genome of a mammoth on an isolated island in the Arctic Ocean, where about 300 animals lived about 4,300 years ago. According to the study, a small island population has lost many olfactory receptors, as well as urine proteins, which can affect social status and mate choice.
According to the researchers, this work provides valuable insight into what happens genetically to a population when it declines.
“We believe that genomes affected by the genomic crisis will have long-term consequences that will impede population recovery,” the researchers write. In other words, efforts to conserve small and isolated populations may be insufficient, overdue due to deleterious mutations. The authors also say that those interested in "resurrecting" animals should expect that the genomes of some mammoths may contain negative, sometimes dire, mutations.
The resuscitation efforts by Church and other scientists are based on DNA extracted from giant hairballs found frozen in Siberia. It is believed that these mainland species became extinct about 10,000 years ago due to climate warming and human activities.
Resurrection and cost of preservation
Bioethics have long debated the ethical implications of reanimating extinct species. New research published in Nature Ecology and Evolution may support the argument against. In their work, scientists argue that attempts to resurrect mammoths can lead to further loss of biodiversity, since the cost of reanimating a dead species is much higher than trying to preserve an existing one.
Scientists estimate that for every extinct species that can be revived in New Zealand, such efforts will result in the sacrifice of the salvation of as many as three existing or living species. This ratio is even worse in New South Wales and Australia, where the resources needed to bring back five extinct species could be used to conserve 42 living ones.
“Given the significant potential for missed opportunities and the risks that a revived species could fill its ecosystem niche, the resurrection process can hardly be justified by the ongoing conservation of biodiversity,” says Hugh Possingham, a professor at the University of Queensland.
“Resuscitation can be useful for inspiring new science and for conservation if we make sure it does not reduce the resources that are allocated to preserve existing nature,” he adds. "However, in general, it will be better if we focus on the many species that need our help now."
Resurrection queue
The woolly mammoth isn't the only candidate for a comeback.
A group called Revise and Restore is working on several projects to remediate the effects of extinction, as well as initiatives to save endangered species. Her flagship project is the restoration of a wandering pigeon, which became extinct in the early 20th century due to relentless hunting and habitat destruction by human forces.
The group developed a checklist of criteria to determine if a species would be a good candidate for return. The criteria fall into roughly three categories: Is it scientifically possible to resurrect a species? Will the revived species survive and thrive in the wild? What are the benefits of bringing a species back to life?
In the case of the wandering pigeon, the goal is to re-establish regeneration cycles in the forests of East America to make them more diverse and productive. Reforestation requires periodic disturbances such as forest fires. Historically, itinerant pigeons have been a major player in natural forest disturbances.
“By restoring the ecological role of roaming pigeons, we can naturally restore and perpetuate reforestation cycles,” the group said in a statement.
Other candidates for resurrection include bucardo, thylacin (marsupial wolf), rheobatrachus frogs, cave lion, Atlantic gray whale, and of course the woolly mammoth.
It seems that there is no simple answer to the question of which species are worth bringing back from the dead. The world is warming, habitats are disappearing, environments are getting dirtier and the biodiversity crisis is deepening. Bringing species back to life, while challenging, could help us rebuild diseased ecosystems.
ILYA KHEL