Science and modern technology have empowered the world with many miracles that were otherwise thought impossible. One such attempt is the resurrection biology, which is to bring the vanished species back to life, commonly known as de-extinction or species revivalism. Not long since the 1990 science fiction novel by Michael Crichton called Jurassic Park achieved sensation throughout the world along with its adopted film series by the same title. Scientists tried to turn imagination into reality by partially succeeding in reviving extinct Pyrenean Ibex in 2003.
Possible Resurrection of Extinct Species In The Future: De-Extinction
There are a number of potential candidates of various species for resurrection, which are being researched. And below is the list.
1. Pyrenean Ibex
Commonly known as Bucardo (Capra pyrenaica), the Pyrenean Ibex was a wild goat that lived in the Pyrenees, the mountain range between France and Spain, surviving on leaves and stems. Due to excessive hunting, their population declined immensely that in 1999 a single bucardo remained. She was a female named Celia and died in 2000 hit by a tree branch, causing the bucardo to become officially extinct. But Celia’s cells were preserved in labs in Madrid and Zaragoza. A group of scientists then injected the bucardo’s cells into goat eggs evacuated of their genetic material. Then they implanted the eggs into 57 surrogate mothers, and seven became pregnant. Six of the seven pregnant animals ended in miscarriages, but one mother that was a hybrid between a Spanish ibex and a goat carried a clone of Celia and delivered it 2.1 kilograms in weight. However, it was only minutes before it becomes extinct again, died with difficulty in breathing due to a gigantic extra lobe in one of its lungs.
2. Woolly Mammoth
The Woolly Mammoth was a species of mammoth that became extinct at least 4000 years ago, possibly due to hunting by humans and consequent shrinkage of its habitat led by climate change. They were roughly the same size as African elephants, while their closest extant relative is the Asian elephant. Researchers believe there are two possible ways to revive the woolly mammoth. One is by cloning, similar to that of the bucardo and another by artificially inseminating an elephant egg cell with sperm cells from the woolly mammoth carcass, which would then produce an elephant-mammoth hybrid and then producing pure breeds after several generations of cross-breeding. But since the sperm of mammals cannot be preserved for too long, this has become a hindrance. However, scientists are trying to synthesize a complete strand of DNA as the mammoth’s genome has already been mapped. A Harvard-based team led by Dr. George Church is currently using CRISPR genome engineering to introduce woolly mammoth genes to elephants to make them adapt to cold temperatures.
3. Passenger Pigeon
The passenger pigeon was a species of pigeon endemic to North America and was known as the wild pigeon (Ectopistes migratorius), which became extinct due to excessive hunting in the early twentieth century. The Revive & Restore project is working to resurrect this species through a series of de-extinction stages. First, they compare the genomes of the Passenger pigeon (obtained from museum specimens and skins) with their closest living relative, the Band-tailed pigeon. Then they plan to edit the genome of Band-tailed pigeon to mimic the traits of the passenger pigeon and breeding this new generation in captivity by 2024 and releasing them into the wild by 2030. So far, they are testing genome editing using Domestic Rock pigeons as a model.
4. Thylacine
Commonly known as the Tasmanian tiger, the thylacine was the largest known carnivorous marsupial native to Tasmania, Australia, and New Guinea. It became extinct in the 1930s and was the last existing species of its family, Thylacinidae. Earliest efforts to clone new individuals of Thylacine began at the Australian Museum in Sydney in 1999 using the high-quality genetic material from specimens collected in the early 20th century. Scientists have already claimed the successful sequencing of the full nuclear genome of Thylacine. They did so by mapping the thylacine genome to their closest extant relatives, the Tasmanian devil. Creating a functional genome is required to continue to the next step of the de-extinction of the thylacine, as stated by researcher Andrew Pask at the University of Melbourne. The scientists are attempting to complete the project by the late 2020s.
5. Quagga
Quaggas (Equus quagga) were a subspecies of Plains Zebras that lived in Eastern and Southern Africa until they became extinct in 1883. The Quagga project was started in 1987 in South Africa to revive the quagga and re-establish them in their natural habitat. By selective breeding from a selected founder population of southern Plains Zebras, an attempt is being made to retrieve at least the genes responsible for the Quagga’s characteristic striping pattern. The project’s first foal was born in 1988, while the first quagga-like individual with visibly reduced striping was born in 2005. As of 2016, they have listed 116 animals out of which six individuals show a strongly reduced stripe pattern and are given the name ‘Rua quagga’ as they are identical in appearance to quagga but have a different genetic code.
6. Aurochs
Aurochs were a species of large wild cattle native to Asia, Europe, and North Africa, and reportedly became extinct in 1627. They are ancestrally related to most modern cattle breeds. Thus many projects have been started to revive them through artificial selection and genome editing. One of the earliest attempts was by Heck brothers, which led to the creation of Heck cattle. However, it is significantly different from Aurochs. Other programs for the breeding of aurochs-like cattle are Taurus Project, Tauros Programme, Uruz Project, Auerrind Project, and many other types of research to breed at least aurochs-like phenotype, if not the genotype.
7. Heath Hen
Heath hen is a presumed extinct North American bird since 1932. The project Revive & Restore is working to bring back Heath Hen and has so far sequenced the genomes, which are being compared to the Greater Prairie Chicken. The team is researching to identify candidate genes that may support to understand its adaptation features. These genes will form the basis for reviving the species. Thus, these genes will be edited into the genomes of Greater Prairie Chickens.
In Conclusion
Numerous research centers and universities around the world are engaged in projects to revive various species of extinct animals. With technologies of cloning, selective breeding, and tools like CRISPR genome editing, it may not take too long to turn such an endeavor into a successful outcome. Efforts are being made not only to revive extinct species but also to increase the population of endangered species. Future potential candidates for de-extinction include the Dodo, the Great Auk, Elephant Bird, Cave Lion, Floreana Island Tortoise, Gastric-Brooding Frog, and many more.
