Popular science - the new God by reason of age

Tom Kirkwood has bravely taken on the much-needed and difficult task of writing a popular synthesis and interpretation of recent progress in the science of human ageing. The book's recent precursors, by Leonard Hayflick and Michael Rose, are well written but unadorned science textbooks.

Kirkwood has worked long and hard to communicate with the general reader. As both a leading theorist in the evolutionary biology of ageing, and much engaged with advocacy, medical science and, broadly, the politics of our ageing societies, he is well qualified. The book discusses ageing, mortality and conceptions of ourselves, the disposable soma theory (the author's own), cell maintenance and reproduction, major degenerative disorders, the menopause, sex differences in average life expectancy, and the potential of genetic medicine. The book ends with approaches to healthy ageing and, as an epilogue, a short story about a society with a much greater life span than today.

The endeavour is wholly admirable and the achievement considerable. There are reasons, however, to urge caution with the speculative and imaginative sections.

The book aims to do more than report the recent advances of science and its present priorities. It engages with human anxieties about ageing and finitude, with conceptions of our material and psychic (although not spiritual) selves, and it speculates about the coming powers of biological science. Outside the imaginative essay, these last are frustratingly truncated. Maybe the aspiration was to write a successful popular science book in the manner of Richard Dawkins, Stephen Jay Gould or Steven Pinker. The claims are large: "Human ageing is at the forefront of scientific, medical and social research and of political thinking as never before ... Time of Our Lives is written to be intelligible to a reader who has no training in science but an interest to know... It even, I hope, has messages for policy- makers." Incidentally, such hubris is sadly undermined by the "provisional criteria" of the 2001 funding council research assessment panels, for they hardly mention "ageing".

Any non-biological gerontologist and diligent reader will learn from this book. The writing is studiously accessible and no knowledge of even basic science is assumed. Supported by extremely well-drawn and annotated diagrams (there should have been more), it provides marvellously clear expositions of cell biology and of specific terms and phenomena that we all should know. A shortlist includes: cell contact inhibition; totipotent and pluripotent cells; cell suicide or apoptosis; DNA replication and repair; and the functions and operation of telomeres. I found the best of the book to be (the artificially separated) chapters seven and eight on cell biology. Here the writing compellingly and instructively guides us through the identification of problems of understanding, theoretical reasoning, the formulation of research questions, and experimental findings; while the leavening references to scientists' egos, vulnerable reputations and scientific fraud are well controlled and enhancing.

Chapter nine is "a rapid tour" of the degenerative diseases, the ageing of individual organs, the endocrine system and homeostatic mechanisms, while chapter ten conveys well the excitement of recent work on cancer cell formation. The next grapples with the still disputed problem of how the menopause might arise through selective survival, chapter 12 synthesises the evidence on dietary restriction and longevity, and the next overviews the still limited understanding of sex differences in longevity.

The author could have been helped more by his editor to suppress the more fanciful analogies, the occasional delectable pleonasm ("the usual cup of tea, served hot in a china cup with handle and saucer"), indulgent autobiographical passages and some irritating unscientific anthropomorphisms ("a profound shift in the psyche of most of the nations of the world"). The more serious worry concerns the radical but far from clear messages about future medical interventions and human longevity.

An ambivalence of purpose is revealed by the two subtitles: the title page specifies the scientific coverage but the dust cover has, "a world authority shows why ageing is neither inevitable nor necessary".

Those themes are explored in chapter five: "Two of the commonest ideas about ageing, however, are wrong... that ageing is inevitable because we just have to wear out (and) that ageing is necessary and we are programmed to die because otherwise the world would be impossibly crowded." I have never encountered the second proposition, which directly contradicts the common evidence in wild populations of periods of exceptionally high mortality through starvation. That aside, the short exposition of these ideas is disappointing and arguably verges on irresponsible sensationalising. Another biologist of ageing, Michael Fossel, recently asserted on BBC Radio 4's Today programme that, within our lifetimes, life expectancy could be about 150 years and within the next century it could be in the millennia. Such claims excite potion peddlers, cause corporate actuaries to jump out of windows and bemuse and raise the hopes of naive listeners.

Kirkwood is too rigorous a scientist to make excessively grandiose or baseless claims, but he does quote The Philadelphia Star in 1913 commenting on Alexis Carrel's claimed demonstration that animal cells in culture reproduce infinitely: "While the good doctor doesn't come right out and say so, he leads us to believe that in future we will be quite exempt from all bodily injuries." Here and there, this book does paint enormously ambitious but vague claims of medical advance by some unspecified time.

If Darwin's socialised religiosity (and fear of the bishop of Oxford) led him to the utmost care in reasoning and demonstration, Kirkwood is at times intellectually carefree. As an exemplar of the immense difficulty and pitfalls of writing popular science, his book will be analysed through many dissertations in the public understanding of science.

This book may come to be known less for the author's brilliant pedagogical passages than for its influence on and use by those who grasp its surface but do not apply critical scepticism to its looser claims.

Tony Warnes is professor of social gerontology, Sheffield Institute for Studies on Ageing, University of Sheffield.