The message that we each hold the reins to success in life’s third trimester is a refreshing tonic in a world awash with quack rejuvenants.

Growing Older Without Feeling Old: On Vitality and Ageing
By Rudi Westendorp (trans. David Shaw)
Scribe, $29.99.

Older and Bolder: Life After Sixty
By Renata Singer
Melbourne University Press, $34.99.

Mention the high cost of sex and you’ll surely silence chatter and raise eyebrows around the drawing room, but for Rudi Westendorp, Professor of Healthy Ageing at the University of Copenhagen, the problem with sex is more monumental than prurient. Put bluntly, it kills you.

To get his drift it helps to envisage yourself as a takeaway food box, loaded with chicken tikka or perhaps a pad Thai. Suffice it to say the good stuff is on the inside and when you’re done the container ends up in that reliquary for the redundant: the bin.

Our good bits are on the inside, too, closeted away in a plump egg or callow young sperm. These gametes hold the DNA blueprint that one day, with luck, will merge with another’s to guarantee our genetic legacy.

But once that progeny is reared to its own reproductive adulthood, the shell – that’s us – becomes a liability. In the ur-state of scarcity we are just another competitor for basics like food and so, rather than threaten the brood, we make a timely exit.

This is the “disposable soma” theory, propounded by British biologist Tom Kirkwood nearly four decades ago, and it does some heavy lifting for Westendorp, who uses it to launch a broadside against the inevitability of cell death and ageing.

When famine gives way to bountiful harvest adults can eat, drink, and get old with little cost to the child, so there is simply no imperative to shuffle off. Twenty-first-century humans produce food for 12 billion and throw a third away, an appalling surfeit that, by Westendorp’s reckoning, makes runaway ageing a reality.

Read my book reviews in full at the Age newspaper here