But oxygen, as every chemist knows, is a dangerously reactive element. Shortly thereafter (in evolutionary terms) another type of cell developed the complementary strategy of respiration, which uses oxygen to extract energy from foods. The atmosphere began to gain large amounts of oxygen when certain cells learned to photosynthesize their food from carbon dioxide and water, with oxygen as a waste product. Early life evolved largely free of atmospheric oxygen, although LUCA, the Last Universal Common Ancestor of current life some 3.85 billion years ago, used oxygen to generate energy. Much of this aboriginal oxygen either escaped into space or reacted with other elements to form mineral oxides. The multidisciplinary text begins with Earth’s primordial environment, in which the main source of atmospheric oxygen was the breakdown of water exposed to ultraviolet light.
British biochemist Lane (University College, London) examines questions of life and death as seen through the lens of oxygen.
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