As another year draws to a close, Steve Jones looks at how many of us are likely to see 100 New Year's Eves.
This deadly time of year is a good time to think about death. In three days, Old Father Time will expire. The year 2010 is hence one per cent away from extinction – the same proportion, as it happens, as of British men who reach their centenary.
That figure, however, is growing. In 2010, the number of centenarians reached 11,600, more than four times the total 30 years ago. At the present rate, that will rise seven times more by 2034. If such progress continues, half the babies born since the millennium will see in 2100.
Is that really possible? Some doubt it. Bannister's four-minute mile in 1954 was pushed down to three minutes 43 seconds in 1999; at that rate, the record in 2110 would be an impossible three minutes. To meet the mortality target, death rates at all ages will have to drop by half, equivalent to the elimination of cancer and heart disease. Even so, other experts think that we still have biological reserves ready to be revealed as medical care progresses.
Demography started with John Graunt in his 1662 book on life and death in London. His causes of demise included "ague" (malaria), "chrisom" (death after baptism), "frighted" (heart attack), "overlaid" (an infant smothered), "rising of the lights" (croup), together with one unfortunate who was "bit with a mad dog" and another dead of piles.
Apart from the dog, each cause tended to affect those of a particular age. Many "died of the thrush, convulsion, rickets, teeth, and worms, or as abortives, chrisomes, infants, liver-grown". One child in three met its end before the age of six, one in 30 made it to 70, and one in a thousand made it to 100.
Nowadays, just 5,000 children under 15 die each year in the UK, a huge drop from the 200,000 recorded in 1900 – in a population about half the size. Medicine and sewers have played a part, but wealth – which brings warmth, food and, best of all, education – is just as vital. The deeper education penetrates, the longer people live. As a result, above a certain level, inequality kills as much as does poverty. The US might be richer than us, but has a lower life expectancy, while Costa Rica does as well as us with a quarter of the wealth.
In Graunt's day, most deaths came from outside (mad dogs included). Here, many such external causes are now under control, but not across the world. In the Third World, infant mortality is far higher than elsewhere, and young people also do badly. A third of humankind is in its teens or early twenties, of which nine out of 10 are in developing countries. Traffic accidents often kill the men, with violence and suicide close behind (in parts of the Americas, these cause almost half of all young male deaths, far more than HIV or TB).
Women do even worse because of problems in childbirth, with more than 250,000 pregnancy-related deaths each year. Botched abortions are the main avoidable killer: in some places, the maternal mortality rate is 100 times higher than where abortion is legal. In South Africa, the fatality rate tumbled tenfold once abortion was legalised. All told, the World Health Organisation says that seven out of 10 young deaths are avoidable.
John Graunt had many heirs. Some of the most energetic were in Scandinavia. They have recently tested whether the huge gains in life expectancy there over three centuries arose because the actual rate of ageing decreased, or from better conditions and improved medical care. It turns out that when the horrors of disease, violence and the rest are discounted, the death rate has been remarkably constant over time, with the same slow and regular increase in the chance of individual mortality with increasing age.
The improvements, in other words, came from controlling those external forces. Now that they have been almost defeated – in Sweden, at least – we are, like athletes, pushing our physical limits, and medical science may not take us much further. The Grim Reaper will swing his scythe almost as effectively in 2011 as in 2010; and on that note, I wish my readers a very happy new year.
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