Mammoths, dodos, and aurochs – oh my! Recent enhancements in genetic tools are helping scientists do the unthinkable—manipulate life and death—by attempting to bring back extinct animals. The possibilities seem endless—but just because something can be done, should it be? Is it a good idea to bring back animals, some that have been dead for thousands of years? Or are efforts better spent on preserving our extant species?
Scientists have engineered multiple methods for de-extinction. One of the most proposed methods is cloning through Somatic Cell Nucleus Transfer (SCNT). This procedure involves isolating the nucleus from a preserved cell of an extinct species and fusing it into a denucleated egg from the nearest living relative. The egg can then be inserted into a surrogate mother of the same species for maturation. In 2003, scientists almost succeeded in using SCNT to resurrect the extinct bucardo, or scientifically named Pyrenan ibex. The bucardo resembles an undomesticated goat. Prior to extinction, skin tissues had been cryopreserved from the last remaining bucardo and a clone was successfully produced from these tissues. Sadly, the clone died minutes after birth due to lung defects, making it the first animal to go extinct twice. Since then, de-extinction has remained at the forefront of scientific research and to date there are 25 or so candidate species on the list to bring back. Our deepest condolences to Jurassic Park fans though, as the old age of any specimens and the degradation of genetic material eliminates dinosaurs from this list.
Another potential method for de-extinction is selective breeding, whereby the closest living relatives of the extinct species are crossbred to reproduce its distinct traits. With each passing generation, the offspring increasingly resemble the extinct species; however, while this method can recreate physical characteristics of an extinct species, the genome remains different from that of the original animal. Furthermore, advancements in genetic technologies have enabled scientists to sequence and assemble the genome of extinct species from degraded tissues. Using the reconstructed sequences as a template, scientists can then insert pertinent genes from an extinct species into the genome of the closest extant relative. Once again, the resulting animal possesses some traits of the living relative but is not identical to the extinct species.
One current project that uses the latter de-extinction methods is the resurrection of the passenger pigeon. While they numbered in the billions at one time, human sport-hunting and habitat destruction led to the loss of this species. Martha, the last passenger pigeon, died on September 1, 1914 at the Cincinnati Zoo. Though genetic material can be obtained from museum specimens, the material is so degraded from age that simple cloning cannot be used. Instead, efforts are focused on editing the genome of the related band-tailed pigeon to mimic the traits of the passenger pigeon. If all goes to plan, the hybrid animal is expected to be ready for breeding in 2024 and could be released into the wild in 2030.
The near success of species resurrection has ignited much debate over whether species should be brought back at all, and if so, how should it be done and how should the species be managed. Some arguments against de-extinction include the huge cost – the price of reviving just a single species could amount to millions of dollars, and at the present time, more than 20,000 species are endangered. These funds might be better spent on preserving current endangered species. In addition, there is the potential to cause harm to extant species and to human health. This is due to competition for limited resources including food and shelter, and the potential to also bring back pathogens and disease. In contrast, those that are pro-species resurrection argue for the possible benefits to the earth in the long-term and the “undoing” of human damage. The technologies used for de-extinction could also be applied to help endangered species, and resurrected species could be used as “flagship species” to support other conservation initiatives.
The idea of de-extinction or species resurrection is both thrilling and frightening, as the implications of this process are unknown. But as science progresses, this once impossible idea could soon be within reach, and the time to ask questions is now.