Oxygen

Lane's argument is that oxygen's role in evolution has always been double-edged: the gas that makes efficient, high-energy metabolism possible for animals and plants is also intrinsically toxic, generating reactive byproducts, commonly called free radicals, that damage cells from the inside. He traces how early photosynthetic organisms first flooded the atmosphere with oxygen, a change that was catastrophic for the anaerobic life that had dominated Earth until then, and argues that the organisms which survived did so only by evolving antioxidant defenses — defenses that later became the biochemical foundation enabling larger, more complex, and more energetically demanding forms of life, including eventually the burst of animal diversity seen in the Cambrian period.

The book matters because it connects deep evolutionary history to a question with direct personal stakes: if oxidative damage from normal respiration accumulates over a lifetime, then aging itself may be, at least in part, a byproduct of the very process that keeps us alive, a hypothesis that has shaped decades of biogerontology research even as later work has complicated the simple version of the theory. Lane also uses oxygen levels to explain striking historical oddities, like why enormous insects and arthropods could exist hundreds of millions of years ago, when atmospheric oxygen concentration was markedly higher than today.

Who should read it

Readers curious about evolutionary biology, biochemistry, or the science of aging will find this a substantive, occasionally technical, but consistently illuminating account of one molecule's outsized influence on life's history. It rewards patience with some denser biochemical sections in exchange for genuinely mind-expanding connections between deep time and everyday biology.

About the author

Nick Lane is a British biochemist and professor at University College London whose research and popular science writing focus on the biochemistry underlying major evolutionary transitions, including the origin of complex cells and the emergence of eukaryotic life.

Caveat: the free-radical theory of aging that anchors much of the book's later chapters was influential but is now considered only partially supported by subsequent research, and the field has since moved toward a more nuanced view of oxidative stress's role in aging.