By Harrison York
Resurrection of extinct species is a topic out of science fiction, but is often theorized to one day become possible. Made famous, or infamous, by the Jurassic Park films, such technology is within the realm of possibility under specific, ideal conditions. While dinosaurs seen in the movies have a much smaller chance of ever being brought back - given that they lived 65 million years ago and insufficient DNA samples have not been found - species from the Pleistocene Epoch, a period of time beginning about 2.6 million years ago and ending around 11,700 years ago, have a much better chance at revival. These animals include woolly mammoths and American horses, which have been extinct for thousands of years. Scientists have discovered DNA from 2,100 plants and 180 animals in soil samples that are viable for replication. Other prospective species for de-extinction from this time period are the dodo, the woolly rhinoceros, and the Irish elk.
But how do scientists resurrect these species? What makes them more viable for revival? Well for endangered species that are not yet extinct, scientists see the possibility of using methods of reintroduction, as in the case of the Caspian Tiger, or selective breeding, like with the Auroch (an ancestor of domestic cattle), rather than cloning or DNA manipulation, to bring back these animals. But for fully extinct species, they turn to ever more science-fiction-like methods.
The gene-editing technology CRISPR-Cas9 is a significant advancement in the endeavor of “de-extinction.” CRISPR stands for “clustered regularly interspaced short palindromic repeats.” Emmanuelle Charpentier and Jennifer A. Doudna, the scientists who developed the method for gene editing, won the 2020 Nobel Prize in Chemistry for their breakthrough. CRISPR works like genetic scissors, allowing biologists to change DNA with high precision and efficiency.
To replicate a species, CRISPR edits the DNA of a “foundation species” to reintroduce the key traits of an extinct species. It is necessary to have a foundation species, as the DNA must be inserted into the nucleus of a replicating cell, which can only be found in living species. This results in an animal that shares DNA and traits with both a modern-day and extinct species. For example, scientists have looked to the Asian elephant, which is most closely related to the woolly mammoth, as a DNA foundation. The gene-editing technology is used to insert the main traits of the mammoth: the shaggy coat, metabolism, and special fat, which let it survive in the ice age thousands of years ago, into the Asian elephant.
Candidates for this resurrection include the Carolina Parakeet (extinct in 1904), the Cuban Macaw (1885), the Quagga (a species of plains zebra, extinct in 1883), and the Tasmanian Tiger (1930s). They are all possible candidates for de-extinction because of their close relation to living species and the quality of specimens that can be used as sources of DNA.
Another major group, which has a higher chance of ultimately making a return, are animals that have gone extinct in the last few centuries due to human actions. There are ample DNA samples for many of these species, and scientists have already brought back one such animal for a short time. The Pyrenean Ibex was a kind of wild goat that lived primarily in Spain and France, in mountainous regions, and went extinct in 2000 from hunting. In 2003, scientists used a frozen skin sample to clone one of the last surviving members of the species from 2000. The team used a domestic goat to incubate the Pyrenean Ibex, which was born alive and genetically identical to the extinct species. Seven minutes later, however, the baby goat, known as a ‘kid,’ died from respiratory failure.
Such failures are caused from complications during the process of implanting cloned DNA into a host embryonic cell. Genes in these cells have anomalies, preventing them from expressing themselves properly in the cloned animals and resulting in high mortality rates around the time of birth.
There is a greater justification for attempting to bring back species that have gone extinct because of human actions. It is seen as a way to right the wrongs our species did to others.
A major, practical reason to bring back mammoths is to fight global warming. The mammoth played an important part in the Pleistocene ecosystem by trampling, grazing, and helping fertilize the environment. They maintained a grassy cap over the northern tundra, but without them, the cap deteriorated and released large amounts of greenhouse gases. Russian scientists have put forth an idea of creating a “Pleistocene Park” to house such de-extinction and climate efforts. They proposed first bringing back the mammoths before possibly moving on to other large mammals. From this park they would be let out into the northern wilderness where they can help bring back the grassy cap of the northern tundra. Already on the reserve are wild horses, bison, and oxen, which have shown promising patterns of grazing and adapting to the environment. The project is another way that we can fix the errors of humanity’s past, as the original people to live in this environment hunted most of the large species to extinction near the end of the ice age.
Mammoth genes mixed with those of today’s elephants could accomplish this goal and allow a biological process to help fight climate change. Knocking over trees and periodically trampling the permafrost, mammoths could ensure that the permafrost layer does not build up, which would keep the grasses alive to help reduce greenhouse gas emissions and prevent warming.
As gene-editing becomes increasingly advanced, it is highly possible that some form of de-extinction can occur. Whether it will be to the extent of bringing back mammoths from the ice age or limited to species of recent extinction, only time will tell. Whatever the outcome, this technology will have wide implications far beyond de-extinction, and will play a greater role in our lives in the future.
Comprehension Questions:
1. What are the benefits of bringing back an extinct species?
By bringing back an extinct species, we can reverse some of the ecological damage the human race has caused. De-extinction may allow us to resurrect species that have gone extinct from over-hunting or habitat loss. Another reason is that these species can help the environment. Currently, climate change is a major issue, and species like woolly mammoths can help slow climate change by reducing the amount of greenhouse gases released from the grassy tundra in northern Asia when they are not properly matted down by grazing animals. Apart from this, scientists will also be able to learn about natural history and the evolution of modern-day species by better observing the animals of the past.
2. Do you think that de-extinction will have more positive or negative impacts on the world?
There is merit to both sides of the argument. The benefits mentioned in the previous question support the prospect of de-extinction, but some possible negative effects include letting the science get away from ourselves and taking this technology too far. If CRISPR technology advances rapidly, there could be negative effects outside of de-extinction that result from gene-manipulation. For species that went extinct before humans, it may not necessarily be our place to try and bring them back. It is also not fair to the returning species if we do not provide them with a habitat they are able to survive in, or if we keep them in a lab for their whole lives. There is also the possibility that the resurrected species would have negative impacts on the new ecosystem. If we are to bring back extinct species, it should be done in a way that improves the world and gives the individual animals a home.
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