Under The Microscope

THE CLOCK OF AGES: WHY WE AGE -- HOW WE AGE -- WINDING BACK THE CLOCK by John J. Medina; Cambridge University Press, 1996; 332 pages; $25 paperback, $39.95 hardback.

Reviewed by Craig Webster

Reading this book reminded me of a ride I took at Disneyland where everything gets bigger and bigger so that you feel you are being reduced to microscopic size. You travel into the human body, then a cell and then see the molecules that make them up. Medina starts with the human face of ageing -- the final moments in the life of his aged mother -- and then takes us on a journey from the outward signs of ageing to the molecular machinery which makes the "clock of ages" tick.

Despite our anxieties of "getting old", ageing starts long before we see wrinkles or grey hair. In fact, ageing is a complex developmental process which starts at conception. Despite taking such a biological view, Medina never loses sight of the individual. The effects of ageing on the lives of many famous people are interspersed through the book with amazing facts about the body: Florence Nightingale was a hypochondriac who spent most of her adult life in bed; each of us contains about 60,000 miles of blood vessels!

We learn that ageing is perhaps not as implacable a force as is often imagined, at least not for some creatures and some populations of human cells. The primitive slime-mold for example seems able to live indefinitely without ageing until a lack of food in the local environment triggers a sequence of events which causes ageing and eventual death, dispersing the next generation further afield in the process. Even in more complex creatures like ourselves, different body parts age at different rates. At least one human cell-type appears capable of immortal life in the laboratory if supplied with the right conditions -- ironically this cell-type is a kind of cancer.

The intriguing question raised by Medina is why do we bother ageing if slime-molds and human cancer cells don't have to? The answer is fascinating and far from straightforward. The body has no single central clock which counts off our life spans but rather is a web of interconnected processes all ticking at different rates. Certain body clocks can trigger a cascade of ageing processes in other cells, but stopping these clocks does not halt ageing as other body clocks come to the fore to replace them. Despite this and the complexities of our 60-trillion-celled bodies, Medina believes we are on the threshold of breakthroughs in longevity research which can only be described as superlative. Some in the field claim that our exploding knowledge of the mechanics of cellular renewal and DNA will see us living twice or three times our current life spans in approximately 30 years.

Craig Webster is currently a clinical researcher in the Anaesthetics Department at Auckland's Green Lane Hospital.