Nurse - What Is Life?

Life is all around us, abundant and diverse, it is extraordinary. But what does it actually mean to be alive?

Nobel prize-winner Paul Nurse has spent his career revealing how living cells work. In this book, he takes up the challenge of defining life in a way that every reader can understand. It is a shared journey of discovery; step by step he illuminates five great ideas that underpin biology. He traces the roots of his own curiosity and knowledge to reveal how science works, both now and in the past. Using his personal experiences, in and out of the lab, he shares with us the challenges, the lucky breaks, and the thrilling eureka moments of discovery.

To survive the challenges that face the human race today from climate change, to pandemics, loss of biodiversity and food security it is vital that we all understand what life is.

It may have been a butterfly that first started me thinking seriously about biology. It was early spring; I was perhaps twelve or thirteen years old and sitting in the garden when a quivering yellow butterfly flew over the fence. It turned, hovered and briefly settled just long enough for me to notice the elaborate veins and spots on its wings. Then a shadow disturbed it and it took flight again, disappearing over the opposite fence. That intricate, perfectly formed butterfly made me think. It was both utterly different to me and yet somehow familiar too. Like me, it was so obviously alive: it could move, it could sense, it could respond, it seemed so full of purpose. I found myself wondering: what does it really mean to be alive? In short, what is life?

I have been thinking about this question for much of my life, but finding a satisfactory answer is not easy. Perhaps surprisingly, there is no standard definition of life, although scientists have wrestled with this question across the ages. Even the title of this book, What is Life?, has been shamelessly stolen from a physicist, Erwin Schrdinger, who published an influential book of the same name in 1944. His main focus was on one important aspect of life: how living things maintained such impressive order and uniformity for generation after generation in a universe that is, according to the Second Law of Thermodynamics, constantly moving towards a state of disorder and chaos. Schrdinger quite rightly saw this as a big question, and he believed that understanding inheritance that is what genes are and how they are passed on faithfully between generations was key.

In this book I ask the same question What is life? but I do not think that only deciphering inheritance will give us a complete answer. Instead I will consider five of biologys great ideas, using them as steps that we can climb, one at a time, to get a clearer view of how life works. These ideas have mostly been around for some time, and are generally well accepted for explaining how living organisms function. But I will draw these different ideas together in new ways, and use them to develop a set of unifying principles that define life. Hopefully they will help you see the living world through fresh eyes.

I should say, right at the start, that we biologists often shy away from talking about great ideas and grand theories. In this respect we are rather different from physicists. We sometimes give the impression that we are more comfortable immersing ourselves in details, catalogues and descriptions, whether thats listing all the species in a particular habitat, counting the hairs on a beetles leg, or sequencing thousands of genes. Perhaps it is natures bewildering, even overwhelming, diversity that makes it seem hard to seek out simple theories and unifying ideas. But important overarching ideas of this kind do exist in biology, and they help us make sense of life in all its complexity.

The five ideas I will explain to you are: The Cell, The Gene, Evolution by Natural Selection, Life as Chemistry and Life as Information. As well as explaining where they came from, why they are important, and how they interact, I want to show you that they are still changing and being further developed today, as scientists all over the world make new discoveries. I also want to give you a taste of what its like to be engaged in scientific discovery, so I will introduce you to the scientists who made these advances, some of whom I knew personally. I will also tell you stories of my own experiences of doing research in the laboratory, the lab, including the hunches, the frustrations, the luck and the rare but wonderful moments of genuinely new insight. My aim is for you to share in the thrill of scientific discovery and to experience the satisfaction that comes through a growing understanding of the natural world.