Reversible Ageing
Targets, Therapies and the Dilemmas of Healthy Longevity
Miguel Moreno 
Preface
A book about the most universal of human experiences, written at the moment when that experience may, for the first time, be becoming negotiable.
For almost the whole of recorded history, ageing was a fixed coordinate of the human condition: something to be endured, interpreted or transcended, but not altered. The biology of the past two decades has begun to unsettle that assumption. We can now measure ageing, identify many of the molecular processes that drive it, and — in laboratory animals — slow, halt or partially reverse several of them. What follows is a careful, current and honest account of that shift, and of the social, economic, ethical and philosophical questions it forces open.
Why now
A threshold was crossed while these chapters were being written. Therapies based on cellular reprogramming — the deliberate, partial rewinding of a cell’s biological age — passed from the laboratory mouse into the first human and ex vivo studies, and the discipline’s vocabulary shifted from cataloguing the damage of ageing towards managing it as a single, potentially modifiable process. The Introduction takes up that institutional moment in detail; what matters here is its bearing on the writing. An account composed five years earlier could have described only promise; one composed five years hence will describe outcomes. This falls in the interval between — where the science is real, its translation uncertain, and the claims most in need of disciplined scrutiny. That interval is the reason for writing now, and it sets the discipline the chapters that follow try to keep throughout: to separate what has been shown from what has merely been announced.
Who this book is for
These pages are written for advanced undergraduate and postgraduate readers, and explicitly do not assume a background in molecular biology or medicine. The aim is to combine the technical density expected of an academic monograph — accurate mechanisms, primary sources, quantitative reasoning — with enough scaffolding that a motivated reader from economics, philosophy, public health, engineering or the social sciences can follow the argument and judge the evidence. Specialists will find the references and the critical apparatus; newcomers will find the bridges.
This is not a longevity manual, a supplement guide, or a brief for living to 150. It takes seriously the distinction, central to the responsible part of the field, between extending lifespan and extending healthspan — the years lived in good health. Where the commercial and rhetorical excesses of “anti-ageing” obscure the science, these pages say so plainly. Roughly seventy per cent of the text concerns the biology and medicine of ageing; the remainder examines the demographic, economic, ethical and philosophical stakes, on the view that a technology capable of reshaping the human lifespan cannot be judged on its mechanisms alone.
The argument moves across five parts, from mechanism to medicine to society; the Introduction sets out that arc and the routes through it that readers from different disciplines might take. What concerns us here is the smaller machinery of reading. Each chapter opens with a short orientation and closes with a brief forward-looking passage that links it to the next — connective tissue, not boxes to be ticked. Several recurring devices appear throughout:
Marks a definition or idea that the rest of the argument depends on. Read these even if you skim.
Collapsible. Expands a mechanism for readers who want the detail; safely skipped by those who do not.
Offers a deliberately imperfect comparison to make an unfamiliar mechanism intuitive. Analogies illuminate; they are not arguments.
Flags a limit of the evidence, a common overstatement, or a result that has not translated from animals to humans.
Simulation boxes present short, runnable pieces of code — usually in R — that reproduce a model or a result in the text. Their code is folded by default; expand it to see, change and re-run the computation. Technical terms link to a hyperlinked Glossary, and abbreviations are gathered in the List of abbreviations.
The choice to publish in a single, interactive HTML format rather than in print is deliberate. A field that revises itself this quickly is poorly served by a frozen artefact: a living document can be corrected as evidence accumulates, can fold technical detail away without discarding it, and can let the reader run the computations rather than take them on trust. The interface offers a light and a dark theme (top of the page); the dark theme is tuned for low-glare extended reading rather than maximal contrast.
A note on sources, tools and method
Ageing research moves quickly, and parts of it are noisy. The account here privileges peer-reviewed primary literature, with citations concentrated in the most recent decade and weighted towards Cell, Nature and their specialist journals, Science, and the major review series. Every reference has been checked against its primary record. Where evidence is preliminary, contested or confined to model organisms, the text marks it as such rather than rounding up to certainty.
The bibliography was maintained and confirmed by me. Of its roughly 250 references, many were settled only after candidate works had been weighed against their most recent alternatives in each section, drawing on several search and indexing services before a precise and appropriate source was fixed; the process took in not only peer-reviewed papers but the grey literature — reports, preprints, institutional and policy documents — wherever these sharpened the statement of a problem or its critical analysis.
A further acknowledgement is owed to the general‑interest press and mainstream media — The Guardian, El País, The New York Times, The Economist, Le Monde — and in particular to the specialist science and technology correspondents whose reporting supplies timely news and contextualised readings of complex developments. Equally indispensable are the dedicated science and biotechnology outlets — Nature News, Science News, STAT, MIT Technology Review, Endpoints News — which provide early signals of scientific shifts, regulatory inflection points and the broader economic consequences of emerging biotechnologies. The selective criteria adopted here leave many such sources outside the final list, yet the quality of their work in science communication must be recognised: it does much to sustain an informed and critically minded public, alert to the marketing framings that magnify partial results and cultivate expectations addressed more to investors than to genuine patients. The selection of sources, the weighing of evidence, the interpretive choices and any errors that remain are mine alone.
The shape of the project was not settled in advance. The proposal from which it grew was negotiated against its own scope, its originality, and a first body of partial sources by which the interest, utility and pertinence of such a work might be judged in the present state of basic and applied science. That appraisal rested on a series of preliminary literature reviews carried out between January and May 2026, which did much to clarify both the feasibility of the undertaking and its standing in a fast-moving field.
The writing itself proceeded with the assistance of a large language model — successive versions of Anthropic’s Claude (Opus 4.7 and 4.8, and Sonnet 4.6), used across the period of composition. Its role was neither incidental nor autonomous. Working in continuous dialogue, I fixed the scope, argument and conclusions of each chapter; the model reformulated prose against that direction, proposed structures and analogies, and performed first-pass checks — verifying citations against their primary records, auditing cross-references, and flagging claims that outran their evidence. Every suggestion passed through repeated cycles of revision and my own judgement before surviving into the text.
A project of this scope and complexity would have been barely tractable for a single author working unaided. The computational reach of these models is what made it manageable: they weigh sources at scale and rework a draft version after version, each pass answering to new parameters and a higher standard of quality. That reach could be put to use, however, only once the prior decisions had been settled: the structure, focus and proportions of the whole, and the graded handling of scientific and technical content — the basic science underlying the relevant technologies — alongside the selection of the sociocultural, economic, ethical and philosophical questions it seemed important to gather into the closing Part V. The choice of a scientific documentation environment, RStudio together with the Quarto publishing system, brought its own preliminary clarifications, chiefly over the formats suited to the intended modes of dissemination and to the versatility envisaged for the resulting materials. Here too the close review of matters open to fine interpretive nuance would hardly have been viable, at this pace, without the agility that these tools — and the language models working alongside them — lend to drafting.
I describe this process in the interest of explicability rather than reproducibility. The first is achievable and, in a work concerned throughout with telling evidence from persuasion, obligatory: a reader is entitled to know how the text was made. The second is not. Generative models are stochastic, their versions are superseded — three were used here across the span of the project — and the writing turned on thousands of small, situated judgements of emphasis, register and omission that no protocol could recover. What is offered is an honest account of the method, not a recipe that would regenerate the result. There is, perhaps, a certain fitness in a study of converging enhancement technologies acknowledging the part that one such technology played in its own making: the principle the later chapters press upon the therapies of longevity — that the genuine power of a tool is no licence to overstate what it has done — holds here as well.
Acknowledgements
My interest in biotechnologies and their social implications dates back to the beginning of my research career as a doctoral student. A decisive stimulus at that stage came from conversations with, and reading suggested by, Enrique Iáñez Pareja, Professor of Microbiology in the Faculty of Sciences at the University of Granada. These interests subsequently broadened in step with the evolving and increasingly specialised debate on gene therapies, the use of stem cells, gene editing, and the enhancement options arising from the convergence of NBIC technologies. Among the colleagues who have actively helped to create opportunities for international collaboration and research through joint projects, I must mention Javier Rodríguez, Francisco Lara, Pedro Francés, and David Rodríguez-Arias, currently in the Department of Philosophy I at the University of Granada. Their work laid the foundations for bringing in collaborators in the field of Moral Philosophy such as Paloma García Díaz and Olga Campos Serena, who for years took part regularly in projects, academic events, and publications connected with many of the themes addressed in these pages.
I am also indebted to other close colleagues and interlocutors — Antonio Diéguez and Pablo García-Barranquero (University of Málaga), Blanca Rodríguez (Complutense University of Madrid), Alberto Molina and Joan Llorca (Department of Philosophy I, University of Granada), Jon Rueda (Institute of Philosophy, Spanish National Research Council, CSIC), and Jorge Enrique Linares (Faculty of Philosophy and Letters, National Autonomous University of Mexico, UNAM), together with other members of the AutAI Project on ‘Artificial Intelligence and Human Autonomy’ (PID2022-137953OB-I00) — for the views and critical analyses they have shared on the development of contemporary technologies with profound societal implications.
These exchanges have taken shape through specialised workshops, shared project-management tasks, thematic technical seminars (notably the TECNEX series), and joint publications and contributions. Such regular interaction generates countless occasions for learning and for conceptual, technical or normative clarification that are difficult to credit individually, yet which, over time, consolidate the benefits of a sustained collaborative ecosystem — one that has proved both stimulating and decisive for the intellectual orientation and methodological standards of the present work.
One final source of qualified feedback deserves mention here: the successive cohorts of postgraduate students enrolled in the Master’s in Biotechnology at the University of Granada. A substantial share of the themes unpacked across the various chapters was subjected to analysis and critical scrutiny through case studies and ad hoc literature reviews.
Granada, June 2026
Miguel Moreno