Population ageing is probably the single most important healthcare challenge the developed and developing world will face in the 21st century. This is because the later part of the human life course is marked by the emergence of a wide spectrum of pathological impairments which increase morbidity and reduce quality of life. The processes driving these increases in mortality and morbidity are often conceptualised as highly complex and multi-causal. Indeed, it has been suggested that there is no human 'ageing process', only distinct, disease-specific mechanisms of pathology. However, humans are not the only organisms within the biosphere to show ageing and the use of cross-species approaches has demonstrated that common ageing processes exist and allowed some of the common genetic pathways controlling them to be identified. Mutants in these pathways either delay or accelerate the development of late life diseases giving rise to extended healthy lives or progerias, respectively. These advances in fundamental understanding open opportunities for a more detailed investigation of the key causal mechanisms underlying ageing and the exploitation of that knowledge for improved interventions in later life.