A Means to an End: The Biological Basis of Aging and Death

For the most part in this book, we will be examining both senescence and death at the level of individual cells, and for a very good reason. Cells are the biological equivalent of the atoms of chemistry, in the sense that they are the smallest thing of which we can say, “This is alive.” It follows, then, that cells are also the smallest thing of which we can say, “This is not alive; this is dead.” Senescence and death in an organism—whether the organism under consideration is itself a single cell, like a yeast or a bacterium, or a complex multicellular organism like a human being—is ultimately a reflection of the senescence and death of individual cells. The outward manifestations of aging are enormously complex, and this has led in the past almost to a feeling of helplessness in studying the underlying processes. Formerly, many of those who studied aging felt that each component of aging—wrinkled skin, cataracts, gray hair, or diminished mental function—must reflect a different underlying mechanism. Yet if we understand that all of the cells in a complex organism like a human being are for the most part

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