Introduction: Wilting leaves and rotting branches: Reconciling evolutionary perspectives on senescence

We humans have long wondered about the seemingly inevitable physiological decline that happens after our maturity. This phenomenon, known as 'senescence', is recognised as the physiological deterioration that results in increasing age-specific mortality or decreasing age-specific fertility at or beyond some age in maturity. But is this phenomenon universal, and is it always the result of the same processes? Although evolutionary theories of ageing exist that suggest that senescence should be universal, empirical data increasingly suggest that senescence may not necessarily be a ubiquitous feature among multicellular organisms, and where it does occur, it is not clear that it is always the result of the same ultimate or proximate mechanisms. In this contributed book, some of the leading scientists in ageing research offer an in-depth, updated understanding of the mechanisms behind senescence, using cutting-edge approaches and species representing a wide evolutionary diversity of life