De-Extinction Coming Soon to Your Genetic Rescue
De-Extinction Coming Soon to Your Genetic Rescue
Charles Darwin's masterpiece On the Origin of Species (1859) asserts that "species and groups of species gradually disappear one after another, first from one spot, then from another, and finally from the world." From a Darwinian perspective, extinction is not only inevitable over deep geological time, but is also, in conjunction with natural selection, a cause of the Earth's astonishing biodiversity. It is only in the late 19th century that we begin to see extinction as something that can be accelerated artificially by mankind, as an environmental problem that merits sustained political attention.
Today, the International Union for the Conservation of Nature (IUCN) estimates that species are disappearing at a rate up to 1,000 times the natural "background" (or baseline) extinction rate as a result of human activities. When rapid anthropogenic climate change is layered on top of long-standing problems such as civil war, industrialization, and deforestation, the prospects for the survival in the wild of large megafauna such as elephants and gorillas, as well as that of numerous amphibian and avian species, are grim. Indeed, when a group of scientists in 2015 used conservative estimates of the current extinction rate, they still found that vertebrates are being lost at up to 100 times the background rate and hypothesized that a sixth mass extinction event is in progress. (Ceballos, et al., 2015)
Against this unceasing stream of bad news, some environmentalists and entrepreneurs are turning to a new conservation paradigm dubbed "de-extinction." Advanced biotechnologies such as somatic-cell nuclear transfer, assisted reproduction, and ancient-DNA analysis today raise the possibility that at least some extinct species could be brought back to life. Theoretically, if adequate samples of viable DNA could be sourced from museum specimens or other fossils, then a species such as the Great Passenger Pigeon could be cloned and a lab-induced embryo implanted in a closely related surrogate species. If this proves unfeasible, the recent development of the CRISPR/Cas9 genomic editing technology opens up the possibility of editing the genome of, for example, an Asian elephant and replacing the excised bits with enough woolly mammoth DNA to produce something that is "close enough" from a genetic point of view to be considered a species resurrection.
Though still in its scientific infancy, the idea that we will be able to bring back species such as the Tasmanian tiger, giant moa, passenger pigeon, or the woolly mammoth agitates the global environmental community. For critics, the focus on de-extinction is primarily a spectacle, a misdirection of our attention away from the real problems of over-consumption and habitat destruction in favour of gee-whiz laboratory stunts.
Economists raise the potential moral hazard inherent in leading the public to believe that bringing back a species could be as easy as saving a few DNA samples to fiddle with later. They point out as well the opportunity cost of choosing to spend money on uncertain high-tech projects rather than on grassroots conservation of extant species and habitats.
From an ethical point of view, many have noted that the animals we are most likely to want to "bring back" are the charismatic species, or speciesâ??like the passenger pigeonâ??that have a well-established extinction narrative that puts the blame squarely on mankind. Whether or not these species are actually the most important for ecological sustainability remains scientifically uncertain (though, in the case of the passenger pigeon, some have hypothesized a positive reciprocal effect between a thriving passenger pigeon population and the American chestnut.)
Finally, one can ask whether it is ethical to bring back a few remnant individuals if there is neither the habitat nor the political will to sustain the species in the wild. From the broadest ethical perspective, extinction has been the bright line drawn between the living and the dead, the boundary that, once crossed, is final. To conjure with moving this line through technology is to threaten our very understanding of nature and our appropriate role in it.
Technically, however, the extinction barrier has already been breached. The Pyrenean ibex (also known as the bucardo), a Spanish mountain goat that has been extinct since 2000, was brought back to life for approximately seven minutes in a cloning experiment that used preserved skin cells taken from the last survivor and a closely related subspecies as a surrogate. (Folch, et al., 2009) The infant bucardo died of a normal respiratory illness, according to the scientists involved.
From a critical perspective, this experiment only updates the techniques used to clone Dolly the sheep, which now may be applied to species for which very recent and well-preserved skin samples exist. It arguably tells us nothing about the viability of bringing back a woolly mammoth, for example. Yet if we accept that science proceeds incrementally and that extinction prior to this point was irrevocable, then the Pyrenean-ibex experiment is a significant development.
Certainly, the prospect of de-extinction is increasingly taken seriously by the science media and by investors. Projects such as Revive & Restore, funded through Stewart Brand's Long Now Foundation, seek to support long-term projects to revive the passenger pigeon and the woolly mammoth. The Genetic Rescue Foundation (based in Silicon Valley) supports science on the possible biotechnological revival of New Zealand's giant moa.
For advocates, de-extinction is not just spectacular science, but is necessary to restore the Earth's biodiversity and repair the global genome. From this perspective, yes, woolly mammoths are charismatic, but they also exerted a significant impact on the development and sustainability of the Siberian steppe (which itself is related to climate change.) Similarly, the thylacine (extinct 1936) was a keystone species in the Tasmanian outback. For this reason, the label "de-extinction" is slowly shifting towards the more accurate "genetic rescue," a policy and scientific frame that puts more emphasis on the environmental benefits of restoring lost genetic information to the planet than on the bells and whistles of CRISPR/Cas9 and other biotechnologies.
From the advocacy position, when it is obvious that mankind artificially accelerated the demise of a particular species, ethics demands that we use our technologies to try and repair this damage, to put back what we carelessly destroyed. Ideally, instead of pitting extinct and endangered species against each other in a zero-sum game, we wisely use our tools to retrieve the past and to sustain the future.
Ceballos, G. et al. (2015) Accelerated modern human-induced species losses: Entering the sixth mass extinction. ScienceAdvances 1(5): abstract available at http://advances.sciencemag.org/content/1/5/e1400253
Folch, J., et al. (2009) First birth of an animal from an extinct subspecies (Capra pyrenaica pyrenaica) by cloning. Theriogenology 71(6): 1026-34.
Amy Lynn Fletcher is an Associate Professor of Political Science at The University of Canterbury in New Zealand. She recently published Mendel's Ark: Biotechnology and the Future of Extinction (Springer 2014) and is an Advisory Board member on social and ethical issues for the Bring Back the Moa initiative (Genetic Rescue Foundation.)
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