There have already been five mass extinctions in this world, and right now, we are living the sixth. With 30 to 159 species vanishing daily, Earth's ecosystem is quickly falling apart. For example, 12,000 years ago, Siberia was filled with dense grasslands and lush steppes that grazing animals like wooly mammoths kept fertilized and healthy with their manure. They maintained the region's low temperatures by eating dead grass and letting the sun reach the spring grass underneath, whose deep roots prevent erosion, and by breaking through insulating snow and allowing the freezing air to penetrate the soil. The light-colored grasses also acted as a sort of mirror, reflecting the sun's rays back into the atmosphere. Once these huge herbivores went extinct, these grasslands became a barren tundra that was home only to scraggly shrubs and mosses. The Tundras and taigas are melting rapidly, releasing tons of carbon dioxide into the atmosphere. As Harvard University's George Church said, "There’s twice as much carbon at risk in the tundra than in all the forests of the world put together."
In Russia, father-son duo Sergei and Nikita Zimov have been running an experiment since the 80s by reintroducing animals like reindeer, bison, and Yakut horses to the Siberian Planes. They observed that these animals lowered the temperatures by as much as 15 degrees Fahrenheit. Bringing back these species could potentially slow down or even reverse these environmental changes. In addition, biological diversity would be extremely beneficial to our planet, as it would mean more natural stability in all of the species affected, and it would make ecosystems more resilient in the face of natural disasters. Because of these benefits, scientists and researchers are trying to bring back a few extinct animals to keep our planet from dying altogether.
On July 30, 2003, a team of French and Spanish scientists managed to bring back a bucardo, a wild deer that became extinct in 2000. Though it was short-lived, as the fawn died after a mere ten minutes, this was a massive success for the scientists. It showed that de-extinction was possible. The cloning was done by depriving the Spanish ibex-goat hybrid's egg of its DNA and implanting the DNA of a dead bucardo in its place. There had been a total of 57 such implantations, only seven of which were successful, and all but one had been miscarriages. Despite the difficulties, this first triumph was revolutionary.
Now, with new technology, scientists can induce adult cells into an embryo-like state, and manipulate them to form either sperm or eggs. The resulting eggs can be even further influenced to form full-fledged embryos. These new methods of genetic engineering will make cloning extinct animals much easier, as the scientists could directly implant the embryos into a surrogate mother, which would make the chance of success much higher than 1/57. If a scientist was able to find a living cell of an extinct animal, it could be made to multiply and form millions of cells, which could then be used to create such an embryo.
However, getting a hold of an intact, living cell of an animal such as the wooly mammoth would be impossible, as it would have either frozen in the tundra or decomposed naturally. Instead, scientists like Insung Hwang plan on focusing on finding an intact nucleus, which would be much more likely to survive. He would then implant this nucleus into an Asian elephant egg that had had its own removed. Of course, this would mean first harvesting elephant eggs, which is a feat that no one has been able to perform just yet. Once the nucleus has been successfully implanted, the egg may divide into a mammoth embryo, which would then be implanted into the mother elephant. If everything went well, a baby mammoth would be born.
Unfortunately, there is a substantial problem with this approach when it comes to birds like the passenger pigeon. Unlike mammals, bird embryos develop inside of shells, and no specimen of the passenger pigeon would contain an entirely grown genome. Using conventional methods of cloning would never work. Biologist George Church had the answer. There are several preserved specimens of the passenger pigeon in museums, and they all contain chunks of DNA. When these fragments are put together, scientists can read the billion letters that make up the passenger pigeon genome. As of now, Church is still unable to put together an entire genome from just these pieces of DNA, but he has invented technology that makes it possible for him to create sizable blocks of any DNA sequencing he wants.
This means that he could theoretically fabricate genes for traits unique to the passenger pigeon, such as its long tail, and splice them into the genome of a stem cell for a band-tailed pigeon using CRISPR, a type of DNA-editing technology. Scientists could then transform these stem cells into germ cells, which they could inject into the egg of a band-tailed pigeon. The birds hatched from these eggs would still be regular band-tailed pigeons, but their eggs and sperm would be packed with this new DNA. Once these birds mated, they would have children that carried the traits put into the DNA. These resulting pigeons could then be interbred, with the scientists hand-picking birds that looked more and more like the extinct species. This method of gene editing to bring species back is also far more realistic than finding a living nucleus, so Church is trying to use this to resurrect the wooly mammoth as well. Of course, breeding and raising these animals until there are enough of them to release into the wild would be a tremendous undertaking, but the monetary cost would be comparable to livestock breeding or conserving endangered wildlife. The expenses could be reduced by using genetic means to make the revived species more resilient, by boosting immunity and fertility. By making these animals more resilient, they are more likely to survive, and the scientists would not have to breed and raise as many. In the end, while we have not entirely reversed extinction just yet, leading scientists such as George Church and Insung Hwang are getting closer to it every day. They have established new techniques to bring these vanished species back to life. Once our planet has finally regained the biological
diversity and functions that these animals took with them when they disappeared, global warming would slow down immensely, and ecosystems could flourish once more.
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