Is ageing inevitable, or can senescence and death be evaded? Large animals and plants always age if they live long enough; even individual cells from their bodies cannot continue living and dividing indefinitely. Whether or not single-celled organisms also age and die, and what relation sex bore to the process of senescence, was the subject of vigorous debate and experimentation early in the last century. In this book, Dr Bell disinters and reanalyzes these forgotten experiments, and argues that protozoan lineages do indeed senesce, as the result of an accumulated load of mutations that can be shed only through sexual reproduction. This unexpected connection between sex and death is the central theme of a book that will interest all students of evolutionary biology, sexuality and senescence.