Wednesday, June 12, 2013

Combating the 6th Mass Extinction

Combating the 6th Mass Extinction

You had your chance.

Over the last 3.5 billion years, an estimated 99% of the species have gone extinct. This is usually countered by speciation, except in the cases of the five mass extinctions that have occurred in the last 540 million years and accounted for 75% of the species lost (Barnosky et al.).  And now, we are currently experiencing the 6th mass extinction.  This is the first mass extinction to be anthropocentric, however, where humans have been the sole cause of the extinction.  As our population has exponentially increased, humans have overexploited natural environments and animal populations, which has led to habitat destruction and increased species depletion. It is hard to pinpoint exactly how many species have gone extinct and how many will go extinct in the future, but researchers have attempted to estimate these numbers.  Currently, between 1.4 and 1.8 million species have been scientifically identified, with an upper estimate of 100 million species possible.  Right now, the extinction rate is estimated to be between 1,000 and 10,000 times higher than the natural extinction rate, which is the rate that species would go extinct without the presence of humans.  So, if the extinction rate is between 0.01 and 0.1% of all species per year and we use the lower estimate of species count of 2 million, about 200 to 2,000 extinctions are occurring every year.  If we use the upper estimate of 100 million species, between 10,000 and 100,000 species are becoming extinct each year (WWF). We are the main cause of this depletion, so is it up to us to slow this extinction and save our planet before it is too late?

            With advancements in genetic technology and knowledge of species, a new idea has emerged known as de-extinction.  Bringing back extinct species was once just a fantasy, but with persistence and determination, this fantasy is slowly, but surely, becoming a reality. There are a few methods for de-extinction, including cloning and genetic engineering.  Cloning began in the 1950s when the first success of cloning amphibians was reported.  After that, mice, cattle, sheep, rabbits, and pigs were reportedly cloned.  However, all of these were clones using early embryo cell types.  It was not until 1997 when the first-ever adult animal was cloned (Edwards et al.).  Dolly, a cloned sheep, was a revolution in the science world, and has opened up new potential for species conservation.  Cloning is now being used in attempt to bring back extinct species.  For example, the gastric brooding frog, an extinct species, is trying to be cloned by inserting its nuclei into eggs of living Australian marsh frogs and barred frogs.  Even though this process is slow because of the reproduction rate of frogs, scientists have still made progress and are hopeful for a positive outcome (Zimmer).

Genetic engineering is another method that scientists have been experimenting with in order to bring back extinct species.  The passenger pigeon is a good example of how this process works. DNA of the last passenger pigeon is preserved, and able to be manipulated, and its modern cousin, the rock pigeon, can be used as the surrogate. The first  
--> step of genetic engineering is to assemble the genome of the passenger pigeon using the preserved remains.  This is then paired with the rock pigeon’s genome to identify and synthesize mutations that are unique to the passenger pigeon.  Once a genome has been created, stem cells are created with DNA and manipulate to form germ cells, which are future egg and sperm cells. These germ cells are then inserted into rock pigeons’ eggs. Once the chicks hatches they will still be rock pigeons, but they will hold passenger pigeon sperm or eggs.  These pigeons are then able to mate to form passenger pigeons (National Geographic Video).  This method could be possible for other lost species such as the giant sloth, the Tasmanian tiger, the saber-toothed cat, the woolly mammoth, and many others.  Now that this technique is no longer a fantasy, the question is not how would we do it, but should we?

An example of how genetic engineering works is shown in National Geographic’s video Recipe for Resurrection.

De-extinction is a controversial process and there are many risks and objections associated with it.  First, animals may end up suffering from the process or from genomic mutations. There will be many failed attempts, in which animals could die and or be severely disabled.  It is hard to know if a new proxy would thrive or not, considering there would be no “parents” to guide the young (Stone).  In addition, new species could be excellent vectors for pathogens or become pests when released into the wild (Sherkow and Greely). Even if previously extinct animals were released into their same habitat, they may cause disorder now.  There is also political controversy over the fact that citizens may see this investment as a priority over curing human diseases (Sherkow and Greely) or protecting habitat for endanger species (Stone). Lastly, de-extinction is something completely different from anything thought possible.  It is manipulative and messes with natural way of things, and that scares people.  However, it is hard to know the consequences of something that has not been endeavored.  

Woolly mammoth picture - museum worker checks hair of woolly mammoth replica
In our society, we are driven by the desire to consume, which has led us to over-exploit species and their habitats. As the sole cause of this mass extinction, humans almost have an obligation to try and bring back the biodiversity lost on our planet.  Biodiversity is a key factor in having healthy ecosystems, which directly and indirectly affect us.  Many of the species that have been lost to extinction were keystone species or provided an important role their ecosystem. Woolly mammoths, for example, were the dominant herbivore in the far north, helping to regulate the tundra grasslands.  Without the woolly mammoth, the tundra lost much of its species diversity and increased in greenhouse gas emission.  The passenger pigeon and the auroch were also keystone species for their habitats (Brand).  In addition to these prehistoric species, those that have gone extinct more recently also provided much support to their ecosystems.  Amphibians, for example, provide excellent pest and disease control as well as provide us with medicinal benefits and biomedical research (Chivian and Bernstein).  However, amphibians are among the most rapidly disappearing group.  About 31% of frog and toad species are threatened or extinct and about 50% of salamander and newt species are threatened or extinct (IUCN Amphibians).  The number of species going extinct is not going to slow unless us as humans make drastic changes.  Using de-extinction could be a key tool in helping to repopulate our earth and restore its biodiversity.

Imagine going to a zoo and seeing a woolly mammoth and saber-tooth tiger. These animals have been mythical creatures for our whole lives, but they could soon be a reality for our future generations.  This new idea is so intriguing and exciting because nothing like this has been accomplished. This new advancement in genetic technology may be expensive, difficult, time consuming, and may not always succeed, but bringing these extinct species back to earth will truly change the world.


Barnosky, Anthony D., Nicholas Matzke, Susumu Tomiya, and Guinevere O. Wogan. "Has the
6th Mass Extinction Already Arrived?" Rev. of Has the 6th Mass Extinction Already Arrived? Nature 3 Mar. 2011: 51-57.

Brand, Stewart. "Opinion: The Case for Reviving Extinct Species." National
Geographic. National Geographic Society, 11 Mar. 2013. <>.

Chivian, Eric, and Aaron Bernstein. "Threatened Groups of Organisms Valuable to
Medicine." Sustaining Life: How Human Health Depends on Biodiversity. Oxford: Oxford UP, 2008. 203-25.

Edwards, J. L., F. N. Schrick, M. D. McCracken, S. R. Van Amstel, F. M. Hopkins, M. G. Welborn,
and C. J. Davies. "Cloning Adult Farm Animals: A Review of the Possibilities and Problems Associated with Somatic Cell Nuclear Transfer." American Journal of Reproductive Immunology 50.2 (2003): 113-23.

"How Many Species Are We Losing?" WWF.

"IUCN Red List Status." IUCN Red List Status.

Sherkow, Jacob S., and Henry T. Greely. "What If Extinction Is Not Forever?" Science
340.6128 (2013): 32-33. Genomics.

Stone, Richard. "Fluttering From the Ashes?" Science 340.6128 (2013): 19.

Zimmer, Carl. "The New Age of Exploration." Bringing Extinct Species Back to Life.

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