Ageing and development: two processes, one history

Development and ageing are usually studied by different communities, with different organisms, tools and vocabularies. Yet the 20 contributions assembled in this theme issue converge on a simple proposition: ageing trajectories are shaped by the way organisms are built. Molecular clocks place the onset of ageing at the end of gastrulation; growth restriction, epigenetic stabilization and the repression of telomerase install, during development, the conditions under which damage will later be tolerated or amplified; and the early environment leaves durable marks on somatic integrity in wild populations. At the same time, the issue shows that development does not determine ageing as an inexorable fate. Organs age as a mosaic, damage initiated in one organ propagates to others through inflammatory and metabolic communication, and some trajectories can be redirected late in life by targeting transmission rather than damage. From these studies, it emerges that ageing is modular and communicative, determining different windows for intervention. This article is part of the theme issue ‘Developmental circuits in ageing’.