The Telomerase Revolution by Michael Fossel, book review

An 'immortality' enzyme could keep us alive - if we want it to

End of the line? The telomerase enzyme allows cells to keep dividing indefinitely (Alamy)

We are used by now to science rocking our world view: a tiny amount of uranium can destroy a city; there is no absolute reference frame for time and space; we are made of cells too small to see that nevertheless contain three billion base pairs of DNA and many thousands of discrete functional chemicals.

But some facts of life seem resistant to being overturned by science. We might have increased the average human lifespan slightly but the ageing process is surely inexorable and irreversible? But no: it now appears that there is a specific programme in living cells that seems to regulate ageing: it is not a matter of wear and tear. Even before the genomics behind this were discovered, there was evidence in the very rare disease of premature ageing in which children die in their teens looking like 90-year-olds.

Michael Fossel is a distinguished American clinician and researcher. The crux around which his potential revolution revolves is the discovery that there are caps – telomeres – on the ends of the chromosomes in all higher animals that shorten every time the cell divides. These caps comprise repeated sequences of DNA, and the loss of a portion of the telomeres every time a cell divides sets a limit to the number of cell divisions possible: as the telomeres get shorter, the cell-repair mechanisms start to fail and the diseases of ageing are the result.

But there are some cells in which the telomeres don't shorten; in these cells, an enzyme called telomerase allows the telomeres to reproduce at the same length every time the cell divides. This confers cellular immortality and is present in sperm, egg and cancer cells. You can see where this is leading. If telomerase were to be activated in normal body cells, it might be possible to halt their ageing process.

But as you read Fossel's account, it becomes apparent that this isn't the story he wanted to write: it might instead have been called Why the Telomerase Revolution Hasn't Happened Yet and Who is to Blame. For Fossel it's "our assumption that change is impossible". But it might just be that, despite the highly plausible rationale for using telomerase therapy to delay ageing and prolong human lifespan, the clinical evidence that it can do this safely is not yet to hand.

Fossel is sure this will happen eventually, however (he is the founder of Telocyte, a biotech company which aims to develop telomerase as a clinical treatment), and he does try to address the skein of problems that would emerge if we could live to 500 years (his highest estimate). But he doesn't address the starkest problem of all: there would be two kinds of human being. I leave you to guess the likely consequence.

At the moment, geneticists the world over are wrestling with the ethical implications of gene editing. The initial goal of this is to correct simple genetic diseases such as cystic fibrosis that involve just a single mutation. I am in favour, but the objectors stress the fact that a single gene change would be passed on forever in the germline. How much greater is the challenge of changing the human lifespan?

Fossel dismisses the common objection first raised by Swift in Gulliver's Travels: the Long-lived Humans would be miserable ancients stuck forever on the same plateau of decrepitude. In Fossel's vision we'll still be fit and vital through most of this span (he doesn't mention whether women's fertile years are likely to be increased by telomerase). But irrespective of the biological, ethical, demographic and economic issues involved in increasing the human lifespan, there are the questions raised by the prospect of any kind of greatly extended life, questions starkly addressed in neuroscientist David Eagleman's themed short-story collection Sum.

In Fossel's gerontological utopia, many more people would live to see the ruin of their hopes in an utterly alien world and the premature loss of children (of which there might be very many). Would anyone really want to live in Fossel's world? If so, I think they should be issued with a copy of Sum before starting the treatment.

Atlantic, £14.99. Order at £12.99 inc. p&p from the Independent Bookshop