Books: It's good news for sea anemones

Time of Our Lives: The Science of Human Ageing

by Tom Kirkwood Weidenfeld pounds 20

Once the noon of life is past, and death casts a lengthening shadow, the chatter about ageing that we have always heard in the background gradually begins to attract our attention. Insidiously, it starts to matter whether we are programmed to die, or whether all animals have the same number of heartbeats in their lifetime. Tom Kirkwood's book, as clear and accessible as popular science gets, is just what we need to dispose of the accumulated lumber of half- remembered half-truths that stand in the way of assessing our prospects.

Time of Our Lives is so good, in fact, that the publishers can be forgiven for the jacket's proclamation "A World Authority Shows Why Ageing Is Neither Inevitable Nor Necessary". This omits the qualification "If You Are A Sea Anemone". Some species apparently do not age; they simply die of being eaten, infected, crushed or otherwise falling victim to their environments. They falsify the idea, popular for a century, that ageing is an inevitable consequence of wear and tear on the cells. The myth of a finite number of heartbeats is a longstanding version of what Kirkwood calls the "fatalistic fallacy". But of the species identified to date as ageless, none are animals.

The belief that ageing is necessary is based on a misunderstanding of evolution which remains extremely tenacious, although its error was clearly identified 30 years ago. Death, it is widely supposed, is necessary for the good of the species, whether to prevent overcrowding or for some vaguer purpose of renewal. But nothing in evolution happens because it is for the good of the species. Natural selection acts on individuals. A population of organisms which obligingly died for the good of the group would be vulnerable to subversion by freeloading mutants. If a mutation arose which blocked the death process, its possessor would enjoy the benefits of its fellows' sacrifice, without paying the price. It would therefore leave more descendants, which would also enjoy the benefits of the mutation they inherited, and gradually the self-sacrificers would be driven out of the population.

A more prosaic reason for doubting that death from old age is necessary to the success of species is that old age is a rare phenomenon, organisms normally being eaten, fatally parasitised and so on before they get that far. However, this also means that organisms enjoy fewer benefits from natural selection as they get older. The more time an organism has to reproduce, the less effect selective forces will have upon the action of genes later in life. Harmful genes that act late are therefore likely to accumulate: Kirkwood refers to them as "genetic dust- beneath-the-cupboard", which becomes visible when the cupboard is moved by environmental changes that reduce death rates earlier in life.

He plays down the importance of this process, which in the opinion of a recent commentator on a paper co-written by Kirkwood, in the journal Nature, does indeed make ageing inevitable. His own theory goes by the catchy tag of "disposable soma". If instant karma doesn't get you, disposable soma definitely will.

By then, however, you are likely to have reproduced, which is all natural selection cares about. Agelessness carries a price: metabolic resources have to be invested in keeping the DNA free from errors. If most animals die before they reach old age, there is no adaptive percentage in creating animals that will last that long. The resources should be allocated to investment in reproduction instead. Different species strike different balances. In the nearest thing to an animal model of rock 'n' roll, the males of one species of marsupial mice stake all on a single blaze of testosterone- fuelled glory, which drives them into a frenzy of mating and fighting over mates. They are left with wounds, stomach ulcers and empty immune systems, as a result of which they almost all die within a few days. We humans are at the other end of the spectrum: built to last, but not too long.

Testosterone does seem to take its toll on us as well. Men tend to live less long than women - about five years, in this country. One exception to the general pattern is India, where the life expectancy at birth of the sexes is almost equal. This could be described as an indirect effect of testosterone: Kirkwood notes that Indian "girls are four times more likely than boys to suffer malnutrition, but 50 times less likely to be taken to a hospital when ill". The reasons why men die younger under less unequal conditions are not really clear, especially when it comes to just how testosterone shortens life. Kirkwood is surely right to depict men as more disposable, though. The marsupial mice are an extreme case of the principle that males can reproduce successfully without remaining around to look after their offspring, but females cannot. One of the distinguishing traits of human female reproduction is menopause, which may leave more than 20 years of active life after the last child is born. This may be a means of maximising the chances that a woman will raise all of her children to adulthood. Jeanne Calment raised her only child to adulthood; her daughter and her only grandchild both died at the age of 36. Mme Calment went on to live to 122, setting the current world record. It will be beaten, Kirkwood assures us, and in the wake of its successors will be a massively expanding tail of people who are remarkably old by the standards of even a generation ago. We want to be among them, but we fear what life at such an age will be like. After Professor Kirkwood's exposition of these awesome matters, it actually comes as a relief that his prescriptions are so modest. Jeanne Calment ascribed her hale longevity to olive oil and port wine. Tom Kirkwood recommends oily fish, red wine, more fruit and vegetables, perhaps a top-up of vitamins C and E, possibly a garnish of trace elements, and simply eating less.

PROMOTED VIDEO
Have you tried new the Independent Digital Edition apps?
Arts and Entertainment
Fans were left surprised by the death on Sunday night's season 26 premiere

TV
Arts and Entertainment
Emma Watson has become the latest target of the 4Chan nude hacking scandal

film
Arts and Entertainment
Lady Mary goes hunting with suitor Lord Gillingham

TV
Arts and Entertainment
Nick Dunne, played by Ben Affleck, finds himself at the centre of a media storm when his wife is reported missing and assumed dead

film
Arts and Entertainment
Lindsay Lohan made her West End debut earlier this week in 'Speed-the-Plow'

theatre
Arts and Entertainment
Artist Nathan Sawaya stands with his sculpture 'Yellow' at the Art of Brick Exhibition

art
Arts and Entertainment
'Strictly Come Dancing' attracted 6.53 million viewers on Friday
tv
Arts and Entertainment
David Tennant plays Detective Emmett Carver in the US version on Broadchurch

tv
Arts and Entertainment
The Doctor goes undercover at Coal Hill School in 'The Caretaker'
tv
Arts and Entertainment
Ni , Rock of Rah, Vanuatu: The Ni live on one of the smallest islands of Vanuatu; Nelson flew five hours from Sydney to capture the 'isolation forged by their remoteness'
photographyJimmy Nelson travelled the world to photograph 35 threatened tribes in an unashamedly glamorous style
Arts and Entertainment
David Byrne
musicDavid Byrne describes how the notorious First Lady's high life dazzled him out of a career low
Arts and Entertainment
Sergeant pfeffer: Beatles in 1963
booksA song-by-song survey of the Beatles’ lyrics
Arts and Entertainment
music'I didn't even know who I was'
Arts and Entertainment
Cheryl was left in a conundrum with too much talent and too few seats during the six-chair challenge stage
tvReview: It was tension central at boot camp as the ex-Girls Aloud singer whittled down the hopefuls
Arts and Entertainment
Kalen Hollomon's Anna Wintour collage

art
Arts and Entertainment

TV Grace Dent on TV
Arts and Entertainment

Music
Arts and Entertainment
Sheridan Smith as Cilla Black

music
Arts and Entertainment
Natalie Dormer is believed to be playing a zombie wife in Patient Zero

film
Arts and Entertainment
Mark Gatiss says Benedict Cumberbatch oozes sex appeal with his 'Byronic looks' and Sherlock coat
tv
Latest stories from i100
Have you tried new the Independent Digital Edition apps?

ES Rentals

    Independent Dating
    and  

    By clicking 'Search' you
    are agreeing to our
    Terms of Use.

    Ebola outbreak: The children orphaned by the virus – then rejected by surviving relatives over fear of infection

    The children orphaned by Ebola...

    ... then rejected by surviving relatives over fear of infection
    Pride: Are censors pandering to homophobia?

    Are censors pandering to homophobia?

    US film censors have ruled 'Pride' unfit for under-16s, though it contains no sex or violence
    The magic of roundabouts

    Lords of the rings

    Just who are the Roundabout Appreciation Society?
    Why do we like making lists?

    Notes to self: Why do we like making lists?

    Well it was good enough for Ancient Egyptians and Picasso...
    Hong Kong protests: A good time to open a new restaurant?

    A good time to open a new restaurant in Hong Kong?

    As pro-democracy demonstrators hold firm, chef Rowley Leigh, who's in the city to open a new restaurant, says you couldn't hope to meet a nicer bunch
    Paris Fashion Week: Karl Lagerfeld leads a feminist riot on 'Boulevard Chanel'

    Paris Fashion Week

    Lagerfeld leads a feminist riot on 'Boulevard Chanel'
    Bruce Chatwin's Wales: One of the finest one-day walks in Britain

    Simon Calder discovers Bruce Chatwin's Wales

    One of the finest one-day walks you could hope for - in Britain
    10 best children's nightwear

    10 best children's nightwear

    Make sure the kids stay cosy on cooler autumn nights in this selection of pjs, onesies and nighties
    Manchester City vs Roma: Five things we learnt from City’s draw at the Etihad

    Manchester City vs Roma

    Five things we learnt from City’s Champions League draw at the Etihad
    Martin Hardy: Mike Ashley must act now and end the Alan Pardew reign

    Trouble on the Tyne

    Ashley must act now and end Pardew's reign at Newcastle, says Martin Hardy
    Isis is an hour from Baghdad, the Iraq army has little chance against it, and air strikes won't help

    Isis an hour away from Baghdad -

    and with no sign of Iraq army being able to make a successful counter-attack
    Turner Prize 2014 is frustratingly timid

    Turner Prize 2014 is frustratingly timid

    The exhibition nods to rich and potentially brilliant ideas, but steps back
    Last chance to see: Half the world’s animals have disappeared over the last 40 years

    Last chance to see...

    The Earth’s animal wildlife population has halved in 40 years
    So here's why teenagers are always grumpy - and it's not what you think

    Truth behind teens' grumpiness

    Early school hours mess with their biological clocks
    Why can no one stop hackers putting celebrities' private photos online?

    Hacked photos: the third wave

    Why can no one stop hackers putting celebrities' private photos online?