On September 7, 1936, at the Beaumaris Zoo in Hobart, Tasmania, a wolf-like creature named Benjamin paced up and down in his cage. As night fell, temperatures grew cooler. The keepers, underpaid and struggling themselves, had forgotten to open the sliding wooden door that would allow Benjamin to move from the outside enclosure into his protected nighttime pen. Benjamin, dehydrated, exhausted, and neglected, died during the night.
The story might sound like a sad but typical event during the Great Depression: with limited resources, many zoos had trouble tending to their creatures. Benjamin’s story was especially tragic, though, because he was the final thylacine—also called a Tasmanian wolf or Tasmanian tiger—on Earth.
But what if we could resurrect him?
The thylacine’s story is just one of the many that Helen Pilcher delves into in her new work, Bring Back the King: The New Science of De-Extinction (Bloomsbury Sigma, $27 in hardback). Alternating between captivating stories about the loss of some of Earth’s most majestic species, and the details of how we could bring them back to life, the book is both a thoughtful analysis of the revolutionary science of “de-extinction” and a consideration of our moral responsibilities towards the ghosts of our past.
Pilcher states in her introduction that her book is about whether or not it is possible to bring extinct species back to life, along with a look at the scientists who are leading the charge. It is also, however, an optimistic look at a science whose possibilities are still entering public consciousness, and is at times a rallying cry for de-extinction. We can either accept that extinction is a part of life, Pilcher notes, or we can fight back — not to create zoo exhibits of lonely animals that serve as spectacles for our curiosity, but to create viable, sustainable populations of animals that could find a new place in living ecosystems.
A major difficulty is that not just any animal can be resurrected: DNA is a flimsy molecule, and once the process of decomposition begins, DNA starts to break apart as well. Though some scientists are hopeful about finding intact DNA of ancient creatures, Pilcher tempers her optimism with skepticism about the limitations of de-extinction science. The current record for the oldest recovered DNA, from a horse found frozen in Canada, is 700,000 years old — millions of years short of the time when dinosaurs roamed the earth.
De-extinction will likely be more a process of recreation than true resurrection, and Pilcher does an excellent job of conveying this messiness without getting mired in too many technical details. For example, she describes how the Neanderthal DNA we have access to is broken and fragmented, sometimes only a few dozen nucleotides long. To produce a Neanderthal genome, researchers had to use reference genomes from humans and chimps to put together a working draft. But is the final product really the Neanderthal genome? Pilcher explains the basic science and leaves this tricky question up to her audience.
Pilcher’s ability to break down the science behind de-extinction in an accessible way is one of the strengths of Bring Back the King. She doesn’t necessarily assume prior knowledge in her audience: for example, she makes sure to define DNA and explain its four bases, and also includes a fair amount of history of the various creatures she describes, along with some of the mass extinctions that have occurred on Earth. From there, she builds on these concepts into even more complicated technologies such as CRISPR, the groundbreaking technology that can edit nucleotides or whole genes with precision.
These chapters would be excellent classroom introductions to the genetic concepts they cover, couched in narratives about fascinating historical species and our hopes to bring them back to life. The text isn’t meant as a comprehensive overview of genetics, but it would make a strong companion to course materials about genetic technologies such as CRISPR or cloning techniques, as the anecdotes and applications would strongly reinforce the concepts.
For example, it might be easier to remember why it’s so much more difficult to clone birds if one were aware of the obstacles that currently prevent us from resurrecting the passenger pigeon. It turns out that the assembly of an fertilized avian egg is a difficult process to interfere with, as there’s no “womb” to receive the product of in vitro fertilization, as there is in mammals. But there may be hope: scientists were able to breed a pure chick from duck and chicken parents — though only after some genetic manipulation of the father’s gonads.
Alongside the scientific detail, Pilcher raises the more important question of our own responsibilities towards animals and species that we re-create. Do we have a moral obligation to bring back species we drove to extinction? What do we do with those species that we do end up resurrecting? Scientific curiosity is not enough — we also have to have some other goal in mind for these animals, in order to ensure that the world we’re bringing them back into is not one of a sterile laboratory or isolated zoo pen. Pilcher’s hope is that we may be able to bring back sustainable populations of animals that would thrive in the wild.
Bring Back the King is not a comprehensive assessment of the state of de-extinction science, but it is an intriguing look at some of the challenges and hopes of de-extinction through separate anecdotes centered on different animals that we could potentially resurrect. The results will not be exactly a recreation of our past, but a hybridization of past and present to create a new future.
- Edit, 23 Jan 2017: Corrected the common name of Thylacinus cynocephalus](http://www.iucnredlist.org/details/21866/0).*