On the Verge of De-Extinction

Coming soon to an ecosystem near you: cloned mammoths, dodoes, and other long-dead beasts. Or semi-cloned, anyway. Scott McLemee learns the difference.

July 29, 2015

So it turns out that -- title notwithstanding -- Beth Shapiro’s How to Clone a Mammoth: The Science of De-Extinction (Princeton University Press) is not a do-it-yourself manual. What’s more, cloned mammoths are, in the author’s considered opinion, impossible. Likewise, alas, with regard to the dodo.

But How Not to Clone a Dodo would never cut it in the marketplace. Besides, the de-extinction of either creature seems possible (and in case of the mammoth, reasonably probable) in the not-too-distant future. The process involved won’t be cloning, per se, but rather one of a variety of forms of bioengineering that Shapiro -- an associate professor of ecology and evolutionary biology at the University of California at Santa Cruz -- explains in moderate detail, and in an amiable manner.

Her approach is to present a step-by-step guide to how an extinct creature could be restored to life given the current state of scientific knowledge and the available (or plausibly foreseeable) advances in technology. There are obstacles. Removing some of them is, by Shapiro’s account, a matter of time and of funding. Whether or not the power to de-exterminate a species is worth pursuing is a question with many parts: ethical and economic, of course, but also ecological. And it grows a little less hypothetical all the time. De-extinction is on the way. (The author allows that the whole topic is hard on the English language, but “resurrection” would probably cause more trouble than it’s worth.)

The subject tickles the public’s curiosity and stirs up powerful emotions. Shapiro says she has received her share of fan and hate mail over the years, including someone’s expressed wish that she be devoured by a flesh-eating mammal of her own making. Perhaps the calmest way into the discussion is by considering why reviving the mammoth or the dodo is possible, but would not be the same thing as cloning one. (And dinosaur cloning is also right out, just to make that part clear without further delay.)

To clone something, in short, requires genetic material from a living cell with an intact genome. “No such cell has ever been recovered from remains of extinct species recovered from the frozen tundra,” writes Shapiro, whose research has involved the search for mammoth remains in Siberia. Flash freezing can preserve the gross anatomy of a mammoth for thousands of years, but nucleases -- the enzymes that fight off pathogens when a cell is alive -- begin breaking down DNA as soon as the cell dies.

What can be recovered, then, is paleogenetic material at some level of dismantling. The challenge is to reconstruct an approximation of the extinct creature’s original genome -- or rather, to integrate the fragments into larger fragments, since rebuilding the whole genetic structure through cut-and-paste efforts is too complex and uncertain a task. The reconstituted strings of genetic data can then be “inserted” at suitable places in the genome of a related creature from our own era. In the case of the woolly mammoth, that would mean genetic material from the Asian elephant; they parted ways on the evolutionary tree a mere 2.5 million years ago. In principle, at least, something similar could be done using DNA from the taxidermy-preserved dodo birds in various collections around the world, punched into the pigeon genome.

“Key to the success of genome editing,” writes Shapiro, “has been the discovery and development of different types of programmable molecular scissors. Programmability allows specificity, which means we can make the cuts we want to make where we want to make them, and we can avoid making cuts that kill the cell.”

Cells containing the retrofitted genome could then be used to spawn a “new” creature that reproduces aspects of the extinct one -- pending the solution of various technical obstacles. For that matter, scraping together enough raw material from millennia past presents its own problems: “In order to recover DNA from specimens that have very little preserved DNA in them, one needs a very sensitive and powerful method for recovering the DNA. But the more sensitive and powerful method is, the more likely it is to produce spurious results.”

Also a factor is the problem of contamination, whether found in the sample (DNA from long-dead mold and bacteria) or brought into the lab in spite of all precautions. Shapiro leaves the reader aware of both the huge barriers to be overcome before some species is brought back from extinction and the strides being made in that direction. She predicts the successful laboratory creation of mammoth cells, if not of viable embryos, within the next few years.

It will be hailed as the cloning of an extinct animal -- headlines that Shapiro (whose experiences with the media do not sound especially happy) regards as wrong but inevitable. The reader comes to suspect one motive for writing the book was to encourage reporters to ask her informed questions when that news breaks, as opposed to trying to get her to speculate about the dangers of Tyrannosaurus rex 2.0.

Besides its explanations of the genetics and technology involved, How to Clone a Mammoth insists on the need to think about what de-extinction would mean for the environment. Returning the closest bioengineerable approximation of a long-lost species to the landscape it once inhabited will not necessarily mean a happy reunion. The niche that animal occupied in the ecosystem might no longer exist. Indeed, the ecosystem could have developed in ways that doom the creature to re-extinction.

Shapiro is dismissive of the idea that being able to revive a species would make us careless about biodiversity (or more careless, perhaps), and she comes close to suggesting that de-extinction techniques will be necessary for preserving existing species. But those things are by no means incompatible. The author herself admits that some species are more charismatic than others: we're more likely to see the passenger pigeon revived than, say, desert rats, even though the latter play an ecological role. The argument may prove harder to take for the humbler species once members of Congress decide to freeze-dry them for eventual relaunching, should that prove necessary.

By now we should know better than to underestimate the human potential for creating a technology that goes from great promise to self-inflicted disaster in under one generation. My guess is that it will take about that long for the horrible consequences of the neo-dodo pet ownership craze of the late 2020s to makes themselves fully felt.


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