Carl Zimmer recently spoke at the TEDx De-Extinction symposium, an assembly of conservation biologists and environmentalists centered on the question of whether extinction reversal is something we should concern ourselves with. Should woolly mammoths stalk the earth once more?
When it comes to bringing bygone animals back to life it is no longer a matter of could, but should. Should we use our scientific and economic resources to restore lost species, many of which were stamped out by our own hands? Many industry experts are toying with naming the current epoch the Anthropocene as a way of coming to grips with humanity’s singular influence on the planet over the last few centuries. By altering the global climate through industrialization and urbanization and by hunting certain animals to oblivion, we have altered the global ecology to such an extent that we are now barreling toward the sixth mass extinction. Current rates have ballooned to as much as 1000x higher than background extinction rates, the majority of which can be chalked up to environmental tragedy.
Is it our duty, ethical or otherwise, to right the wrongs already committed? But alas, there is more than just resurrection of species to consider. Restoration of habitat is just as important. If the environment these once-thriving animals left is also not brought back, these attempts might very well be futile. Our new friends may quickly drift back into retirement. The older the species and the more removed the ecosystem is from its historical counterpart, the more critical this concern becomes.
Likewise, is behavior something that can be restituted? Even if we could compile bit-for-bit working copies of a species’ genome, how would we ever know if its behavior matches that of its extinct predecessors? After all, animal behavior is moderated by both environment and genes, and if we can only recover the latter, have we really achieved our goal? What reference could we check against? Most of what we rely on for our behavioral understanding of long-extinct species is locked up in non-scientific observations recorded in literature and crude note-taking by amateurs. Would the 21st century Tasmanian tiger really be the Tasmanian tiger of yore?
There is also health risk to consider—to humans and non. De-extincted species might become new vectors for transmissible diseases. Moreover, the old genomes of creatures like the passenger pigeon, the great auk and heath hen may prove defenseless against today’s viruses and bacteria that have evolved greatly since their passing. Rewilding these species could instead be a death sentence for them and could reintroduce medical horrors for us. That is, unless we were to insert the proper mutations into their reconstructed genomes by way of gene editing. This, as you can well imagine, is no small task, especially given the nascency of gene therapy.
Finally, what are the candidate species that provide the lowest chance of risk and highest chance of smooth assimilation? Some lay completely outside the bounds of possibility, of course. DNA fragments over time and has a shelf life much like radioisotopes. The bi-stranded helical structure of DNA prefers cold, dry, insulated environments, which explains how the now iconic Ötzi, a 5,300 year-old human fossil entombed in a glacier 10,530 ft high on the Alps, yielded intact DNA. We’ve even plucked nuclear DNA from a 700,000 year-old horse fossil, thanks to it being preserved in permafrost. This likely approximates the upper limit of usable DNA we will get our hands on, leaving Jurassic Park-like fauna, along with the overwhelming majority of all extinct species reaching millions of years in the past, off the table for now.
However, animals like the woolly mammoth, which may be recovered via frozen nuclei, the Red River giant softshell turtle, Steller’s sea cow, Tasmanian tiger, gastric brooding frog and passenger pigeon are all real possibilities. We have full nuclear and mitochondrial DNA for both the thylacine (Tasmanian tiger) and the gastric-brooding frog. For older species in which we have only fragments, the task will be more challenging but not impossible.
Yet the central question remains: should we use science in this way—to give these animals a second chance? The debate goes beyond what is noble as a good case has been put forward that de-extincting niche players can help conserve endangered species as well as counter global warming, for example, by reseeding Siberia with mammoths. This is not a zero-sum game and in this sense de-extinction can be thought of as a parallel effort of conservation biology.
The hardest questions to answer given our current understanding of past and present bio-ecology involve what roles and functions the species would fill in their new environment, whether their reintroduction would have a positive or negative impact on existing food chains and local and macro-ecologies, and whether we should instead commit all resources to keeping endangered species alive. Listen as Carl Zimmer works through some of these gritty issues at the TEDx conference below.
UPDATE: Here’s an excellent podcast for getting up to speed on the current status of de-extinction efforts and the attendant ecological and ethical implications. Guests include Carl Zimmer, Mike Archer (paleobiologist) and Wendell Wallach (bioethicist).
Feature image courtesy of Royal BC Museum in Victoria