Greek mythology tells the tale of Prometheus, who defied the gods to bring humankind the knowledge of fire and how to use it. Prometheus was harshly punished by Zeus, yet the Greeks regarded fire as the source of all art and science. This narrative resembles the Biblical Fall; while the fruit of knowledge comes at a high price, it is a precondition for becoming fully human.

A couple of thousand years later, in 1818, Mary Shelley published her novel Frankenstein; or, The Modern Prometheus. The story showed what might happen if human pride and ambition overreached themselves in a bid to emulate God. At the time the book was written, scientists had just discovered that they could make a dead frog twitch by delivering jolts of electricity to the corpse. There were theories that a divine, life-giving force might have been discovered.

Taking inspiration from Jewish legends about golems, Mary Shelley created a terrifying scenario in which a scientist applied that force without really comprehending or being able to control it. For the book is also the story of a scientist who refuses to accept responsibility for his work – a man who flees, leaving the newly awakened monster to his fate. It’s clear that if Victor Frankenstein had had the courage to stay and take care of his creature, tragedy could have been averted.

One hundred and seventy-five years later, in 1993, the film Jurassic Park showed resurrected dinosaurs running amok because scientists had let their enthusiasm and curiosity get the better of them. The moral that revolutionary knowledge and godlike powers can cost us dear has been thoroughly rammed home. At the same time, the idea persists that we would no longer be human if we lacked that very drive.

It may sound silly to let yourself be influenced by ancient myths today, yet I believe these stories were the reason for my mixed feelings when I heard that scientists were working towards resurrecting extinct animals with the help of modern gene technology.

My first reaction was one of boundless enthusiasm. I felt like an excited ten-year-old at the thought of being able to see a real live mammoth, or a dinosaur, or any of the creatures that have died out in the course of history – at the idea of actually seeing them move and hearing the sounds they made. What does a mammoth smell like? Do dinosaurs bob their heads as they walk, like today’s birds? Do aurochs low like cows?

Scientists are also trying to restore many less spectacular creatures that are at least equally fascinating. The Australian gastric-brooding frog is one example. The female frog would eat her eggs and let them develop from frogspawn into baby frogs inside her belly. Then she would regurgitate a litter of croaking froglets ready to meet the world. This genus died out in the 1980s, struck by a fungal disease that continues to threaten many other types of frog. The project to resurrect the gastric-brooding frog has been dubbed “Lazarus”, after the story of how Jesus brought a man back from the dead.

All the projects I describe in this book began with the thought: “Wow! We could actually do this. Of course we’ll give it a try!” They are driven by the same enthusiasm and curiosity that makes a child learn the name of every dinosaur that ever walked the earth, or an explorer set sail for the distant horizon. It’s easy to be swept along and to feel the same effervescent energy.

My second feeling was one of age-old unease. Is this really a good idea? What if it has unforeseen negative consequences? Would it mean unleashing forces that we would later be unable to control? This unease is not born of mythology alone. There’s no shortage of examples of well-intentioned people who have wreaked havoc on the natural world.

One example – absurd from today’s perspective, but a good illustration – is afforded by Eugene Schieffelin, an American who began releasing European birds in New York in 1890. His aim was to make sure that every single type of bird mentioned in the works of Shakespeare was represented in the United States. Schieffelin was a member of a highly respected scientific association, and his project enjoyed widespread support. It was associated with the acclimatisation movement, which actively dispersed species from continent to continent.

While most of the species died out within just a few years, the hundred starlings released in Central Park multiplied rapidly. They displaced large numbers of native birds as they spread out over the continent. Today, the United States has about 200 million European starlings, creating problems both for the ecosystem and for farming. And all this sprang from the worthiest of aims – biological and cultural enrichment.

Each day as a science journalist brings me examples of how scientific curiosity and zeal are improving life for almost all human beings. These range from the technology we use to the medicines we take, the food we eat and the clothes we wear. I am genuinely convinced that the world is getting better all the time, and that the main reason for this is new research. And yet – for all my optimism and confidence in the future – that uneasy feeling in my stomach persists.

Gene technology and biotechnology are developing at the same rate today as information technology did in the 1990s, possibly even faster. This means scientists can already do things considered impossible just a few years ago. It also means they will very soon be able to achieve things that seem impossible today. Recreating the mammoth may be one example.

New methods for restructuring genetic material in everything from bacteria to human beings have created a whole new world of opportunities, but also of fears. This potential seems all the more terrifying because of its novelty. Just as with the advent of computers, we lack a context for this development that could help us understand it and predict where it will lead.

I believe that genetics and biotech are going to transform our society in just as fundamental a way as digital technology has done. I am also convinced that most of that change will be positive. At the same time, major problems are bound to arise. I don’t think we will make any progress unless we take this fear seriously, examine it, and analyse the cases in which it is relevant. This means looking at the practical aspects: how can we avoid making the same kind of mistakes as Victor Frankenstein or Eugene Schieffelin? But it also means examining the philosophical side: how will the capacity to manipulate life affect us as human beings, our culture and our society?

The third thought that came to mind when I first heard about these projects was that the desire to bring extinct creatures back to life sprang from nostalgia, a yearning to return to a lost world. I have met old men who seem to be dreaming of immortality. Four of the keenest researchers in this field are in their 60s. I have also met Ben, not yet 30, who has resolved to devote the rest of his career to resurrecting an extinct species of pigeon.

All of them have a deep-seated feeling that the world and humanity have lost something important, and that there is a chance we could recover it. Exactly what it is we have lost, and when it happened, are questions to which they all have different answers.

Those three emotions – enthusiasm, fear, and nostalgia – have accompanied me throughout my work on this book. However, I have also realised that there is more, much more, to tell about the scientists who are determined to try to bring creatures back from the dead. And there is another aspect to their efforts that is arguably even more significant.

All the scientists I have spoken with seek to make the world a richer, wilder, and better place. They are convinced that reviving extinct fauna can contribute to such a future. Henri, who aims to breed an aurochs; George, who is trying to piece together a mammoth; William, who wants to see majestic American chestnut trees again; and so on. All of them are aiming to create a whole species that can be returned to nature, not merely a single individual.

The sole exception is Jack, who is trying to recreate a dinosaur. That experiment is different from all the rest, so if the only reason you picked up this book was to read about the chances of there being a real-life Jurassic Park, I suggest you go straight to Chapter 13. I hope you will find it so fascinating that you will come back to the beginning. And if you want to know more about the various projects, there are sources and notes at the back of this book and on the associated website.

It remains to be seen how resurrecting a species would work in practice. Essentially, all the projects I refer to in the book depend on at least one major scientific breakthrough in the future if they are to succeed. However, such breakthroughs are now coming so thick and fast that it is hard to see this as much of an obstacle.

What really fascinates me in the idea of reviving extinct creatures is that the mere thought of it expands my horizons, opening up dazzling new possibilities. Yet there is a fundamental question we need to ask ourselves collectively, and that is how far human beings should go in controlling nature. Now that we are on the threshold of being able to recreate lost creatures, reconstruct wild species, create entirely new forms of life that would never have come into being unaided – what do we do with that knowledge?

Excerpted with permission from The Re-origin Of Species: A Second Chance For Extinct Animals, Torill Kornfeldt, translated from the Swedish by Fiona Graham, Context.