Children are getting taller. There's no doubt about it. Look at the towering 10 and 12-year-olds in the school playground. And although some of those adult-size youngsters buying child tickets for buses and underground trains are on a scam, they aren't all. It isn't just the up-and-coming generation. The human race has been reaching higher and higher for centuries, but the sheer speed of our upward growth has only been dramatically obvious since proper record keeping began.
We all know that we'd never squeeze into those pint-sized suits of armour which these days fail to loom menacingly in the corners of castle halls, and we can only wonder at the short stature of whoever used to walk through Norman arches. But it isn't until you hear that the average teenage boy is now around nine inches taller than someone of his age would have been in 1837, that the scale of what has been happening is apparent.
That figure comes from an internet survey of 5,000 seven to 16-year-olds in England, Wales and Northern Ireland, released by the Office for National Statistics and the Centre for Statistical Education at Nottingham Trent University, who compared the average height of a 15-year-old boy today, at 5ft 8in, with that of children working in factories in 1837.
According to Peter Hindmarsh, reader in paediatric endocrinology at Great Ormond Street hospital and University College London, there has been evidence of a generally upwards trend throughout the history of the human race, although with the odd downward dip usually thanks to rampant disease. But it is hard to be precise about size, because the skeletons discovered are usually those of the best nourished and most affluent individuals of the era. In the past couple of hundred years, however, we have been compiling much more precise data.
"There have been quite marked secular trends [a steady increase] in height in western Europe from the 19th century. The best documented are in the Scandinavian countries from about 1870 onwards where the average increment is about 1.5cm per generation," he says. Given 20 years or so for a generation, this suggests 7.5cm a century, or around three inches.
We are what we eat, and our height is strongly linked to nutrition. The changing stature of various groups whose eating habits have changed with migration bears this out very strongly. The first generation of Japanese born to parents who had moved to California virtually immediately mimicked the growth patterns of American children. Something similar is happening to the children of Asian groups in the UK, although more slowly. It is not only migrant Japanese who are growing taller - there was a major growth spurt among children in the indigenous Japanese population between 1950 and 1990, which some experts have put down to increased milk consumption after the second world war. Interestingly, all the increase was in leg length, which is the most rapidly growing part of the body in early childhood.
Height is one of the rare things which is not genetically determined. The children of affluent parents in the developing world grow just as tall as those in the developed world. Height is dependent not on the quantity of food we eat as babies and children, but on the quality - the amount of protein, fats, vitamins and minerals. The red-meat eaters of Australia and the United States tend to breed tall children. Poor diet and exposure to infection keep children small. Infections can lead to gastrointestinal damage, which prevents babies and small children absorbing the nutrients their bodies need for bone growth. At the very least, they lead to loss of appetite.
Bigger babies are likely to grow taller, but mainly because their size at birth indicates that their mother has been well-nourished during pregnancy. It is birth weight, height and weight of the mother, in fact, that makes the most significant difference to the height of the child.
But also significant is the attention the mother pays to the child. This is not as mysterious as it sounds - the more time the mother has to spend on the child, the more likely she is to feed him or her well and encourage his or her appetite. So first-born babies do better, because there are no small siblings to make demands of the mother, and babies born into affluent families do well, because there is money for good food, less chance of infection and usually fewer children or more adults with the time to fuss over them.
As we in the west grow more affluent and are better fed, will we, like Alice Through the Looking Glass, find ourselves outgrowing our houses as we have already outgrown the Norman doorways? Maybe not. "In the UK we are slowing down if anything," says Peter Hindmarsh. "There is probably a limit to how tall we can get. The trend has virtually stopped in Scandinavia. The only nation where it continues to rise is in the Netherlands." But why the Dutch are continuing to grow taller, he does not know.
And there is something else. What makes us think size matters? There is evidence that tall people are more likely to suffer heart disease in later life than short people. It's a high price to pay for the ability to reach the top shelf. "It may be," admits Hindmarsh, "that we are swapping one thing for another."
