‘Extinction is not forever’ was the phrase that caught my attention when I first heard about the developing initiatives to bring back extinct species. It was truly a revolutionary thought! The chance to consider de-extincting species is only possible as a result of a remarkable decrease in the cost of reading and writing DNA, together with the creation of a set of innovative tools for manipulating the structure of DNA. The possibility of de-extincting species is being taken seriously and IUCN has commissioned a working group to develop guidelines for the conservation application of de-extinction.

The emerging field has drawn intense journalistic and public interest, with philosophical, ideological and practical objections and assertions battling over something that has not yet happened. Into this commotion comes the first book I am aware of that takes on the issue seriously. A short book, it sets out to provide a road map for de-extinction, in three parts: how we might make the decision about what species or traits to resurrect, how this might be done technically and biologically, and how to manage populations of engineered individuals once they are released into the wild.

This book has been widely reviewed and the author widely interviewed. Everyone loves mammoths and enjoys playing with the idea of seeing their lumbering, impressive forms back on earth, and Shapiro is a mammoth expert. But the important thing to realize is that what is being talked about by Shapiro and others is not really bringing back mammoths but bringing back mammoth traits such as subcutaneous fat and more hair and the ability to survive arctic winters. The IUCN working group on de-extinction is aware of this, and their draft definition of de-extinction is: ‘… to apply to any attempt to resurrect some proxy of an extinct species or subspecies (hereafter “species”) through any technique, including methods such as selective back breeding, somatic cell nuclear transfer (cloning), and genome engineering’. So what we are really talking about is not mammoths per se but mammoth-ness—the qualities of being a mammoth. As such the de-extinction is at the genetic level of biodiversity rather than the species level.

But after much discussion about the details of cloning, genetic architecture and DNA functioning and the study of ancient DNA (the author's speciality), in the end what Shapiro wants is ‘… not to create monsters or to induce ecological catastrophe but to restore interactions between species and preserve biodiversity’ (p. xi). Here is where the book is weakest. Not an ecologist, Shapiro's desire to restore these interactions is based on an assumption that the mammoth ecosystems (and some claim there were such) have remained the same and will resume their previous functions with the return of the now mammoth-endowed elephants. Clearly this is a contentious point of view and worth the serious consideration of ecologists. The uncertainty around this topic is not a sideshow but vital if the ecological functioning of mammoth-like elephants is the measure of success for de-extinction of these beasts.

So read the book. It will make everyone think, will make some mad, others inspired, and hopefully will educate all conservationists to the extraordinary potential opportunities, good and bad, that de-extinction presents.