It has long been widely believed that the upper class look down on the middle and lower classes. Now science has established that this is literally, as well as figuratively, so. Thirty years of research by leading economists, biologists, historians and demographers has confirmed the towering status of the high and mighty.

The Changing Body, to be published next month by Cambridge University Press, concludes that there is a clear link between height and earnings. Increases in both, over the past 300 years, are greater than over the three preceding millennia, demonstrating that the changes are too rapid to be evolutionary. And the secret lies in nutrition.

Some 200 years ago, differences in height between working-class and upper-class people were "really substantial", said Sir Roderick Floud, a leading economic historian and one of the leaders of the team behind the book.

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In the late 18th and early 19th century, a comparison between boys from the slums of London and boys at Sandhurst Royal Military Academy – the children of peers, clergymen, naval and army officers – showed that between 90 to 95 per cent of working-class boys were shorter than upper-class children.

"Those upper-class children were well fed and rich, but still significantly shorter than boys today," Sir Roderick said. "But working-class boys were so short that if you took them into the doctor's surgery today, you'd be whipped off to nearest hospital for child neglect."

In the 1780s, the average height of a 14-year-old working-class child was 1.3m, while an upper class child was " significantly taller" at 1.55m.

As health services, nutrition, sanitation and education have become universal, upper-class children have continued to grow taller, but at a slower rate than working-class children. The difference between the upper- and working-class adults has narrowed to less than 0.06m.

Regional variation also plays its part. Two centuries ago, the Scots were 2.3cm taller than those living in southern England, while Norwegians were among the shortest nations in Europe. Today the Scottish, averaging 1.73m for an adult male, are shorter than those living in south-east England at 1.75m, while the Norwegians are the second tallest nation in Europe, surpassed only by the Dutch.

Professor Bernard Harris, one of the book's authors, said: "Improvements in diet and sanitation in the South-east have outstripped improvements in Scotland, reflecting the broad pattern of economic and social change over the last 200 years."

Sir Roderick said: "The average height of countries across Europe, or regions within a country, shows how well they are doing. If you rank countries by height, it's close to ranking them by gross domestic product."

The link between height and earnings is borne out through the research, as taller people tend to be more successful, while economic success in turn breeds taller people.

"Are you paid more because you're taller, or are you taller because you come from a richer family?" Robert Fogel, the Nobel prize-winning economist and co-author of the book said: "There is some evidence that employers and voters prefer taller to shorter people. One way of thinking of it is that we like to look up to our leaders."

Similarly, the longevity trend shows "no sign of diminishing", according to Fogel – despite concern about whether there will be enough resources to sustain future populations. Some half of teenagers today can expect to live to be 100. Fogel predicted that future generations will live to 130. "My great-great-grandchildren will be asking: 'Is it really true that people born in the 1930s only lived to be about 80 years old?' One of the things we discovered was the very large increase in life expectancy, at two years per decade."