"The question of what it means to be alive has flowed through four centuries of scientific history like an underground river," writes journalist Zimmer (She Has Her Mother's Laugh) in this stimulating inquiry into biological fundamentals. He explores scientific phenomena that challenge simplistic concepts of what life and intelligence consist of (such as the notion that life is "something that sustained itself through chemical reactions"). Among his subjects are a girl who was declared brain-dead in 2013, but went on growing for years; hibernating bats whose metabolisms all but stop; and hypotheses about what creatures might lurk in the half-frozen sea of a moon of Saturn (namely, life that wouldn't need sunlight). The author travels to laboratories, caves, and botanical gardens for colorful depictions of cutting-edge experiments, as with his reportage on a slime mold without neurons that "followed the trail of sugar into the cul-de-sac and hit the acetate wall. But it did not give up its search. It sprouted tentacles to either side." Zimmer discusses scientists' various definitions of life as well as different schools of thought, such as "vitalists," who believe life has a purpose, and "mechanists," who believe that life is "made up of parts that work together, much like a clock." The result is a pop science tour de force that extracts provocative insights from life's oddities. Agent: Eric Matthew Simonoff, WME. (Mar.)

Our understanding of life is mostly intuitive, maybe prewired. Respected science writer Zimmer (A Planet of Viruses, 2011; She Has Her Mother's Laugh, 2018) diligently tackles the true definition of life. His curiosity and research lead him to a strange biologic limbo, "life's edge, to the foggy borderland between the living and the nonliving." Zimmer profiles creatures (rotifers, tardigraves, nematodes, multiheaded slime mold) capable of suspending their life, then, when conditions allow, "resurrecting" themselves. In the fabulous chapter, "Half Life," he considers the earth's virome, providing clarity on COVID-19 and the viral populace at large. A mere spoonful of soil or liter of seawater holds a greater number of viruses than there are people on the planet. Zimmer suggests viruses "straddle" the boundary of living, while one scientist believes they have "a kind of borrowed life." Other fascinating topics include assassin proteins, parthenogenesis, primate thanatology, and astrobiology. Five hallmarks of life are delineated: metabolism, homeostasis, information gathering, reproduction, and evolution. NASA has offered a definition, "Life is a self-sustained chemical system capable of undergoing Darwinian evolution." Succinct, but hardly inspiring. The foremost question in biology--What is life?--remains strangely unanswered. For now, Zimmer invites us to observe, ponder, and celebrate life's exquisite diversity, nuances, and ultimate unity.

Journalist and author Zimmer (A Planet of Viruses) addresses the question of what it means to be alive; not so much in the philosophical sense, but by exploring the boundaries of the definition of "alive." Biologists have been refining the definitions of life through the centuries as they learn more about the diversity of living things. When does a new human life begin? What physiological signs mark the end of a life, beyond which there is no return? And, more broadly, what are the minimum essential characteristics something must possess to be considered a living thing: metabolism, response to stimulus, self-regulation, reproduction, ability to evolve? And is life a property of an organism, a species, or a single cell, or perhaps even smaller? From where did life emerge from non-living matter? If we were to look for life on another planet, how would we know we had found it? By profiling researchers working on these inquiries, Zimmer shows the complexity of reaching a single answer as each proposed definition has its edge cases that provide challenging counter-examples. VERDICT A fascinating and well-written mapping of the edges of biology, which will have broad appeal to nonscientists.--Wade Lee-Smith, Univ. of Toledo Lib.

A master science writer explores the definition of life. After reviewing the history of the concept of life, Zimmer recounts his global travels interviewing scientists who have made dazzling discoveries. However, when it comes to defining life itself, they cannot improve on the Supreme Court's view of pornography: They'll know it when they see it. The author quotes Frances Westall and André Brack, who wrote in 2018 "that there are as many definitions of life as there are people trying to define it." In the end, writes Zimmer, "to be alive is not to be dead." Despite the countless possible definitions, most biologists agree on a few hallmarks: Every creature that lives must metabolize (eat and digest), gather information about the surroundings, maintain homeostasis (keep the internal environment steady), reproduce, and evolve. Zimmer gives ample space to nitpickers who point out exceptions, and a few chapters record interviews with scientists exploring each of these hallmarks. None answer the author's big question, but readers will not complain because Zimmer is such an engaging communicator. Confronting a possibly unanswerable question, the author explores its history, an eye-opening review of three centuries of research by intensely curious, obsessive, often obscure scientists who contributed to many revelations about the amazing attributes of life, when they weren't deluded--e.g., 18th-century vitalists, who believed that "life contained a vital force that endowed matter with self-directed motion and the power to generate new complex bodies." Veteran readers will not be surprised that Zimmer's conclusion describes efforts to create life in the laboratory, a process whose possibility was suggested a century ago and whose first and many subsequent attempts produced headlines and increasingly complex but lifeless organic material. The author leaves no doubt that this century's dazzling advances in genetics, biochemistry, DNA and RNA manipulation, and lipid membrane formation will bring home the bacon. An ingenious case that the answers to life's secrets are on the horizon. Copyright (c) Kirkus Reviews, used with permission.