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Credit: Getty Images) Zhang Juncai, one of China's tallest men, comparing his hand with a seven-year-old boy in 2004 (Credit: Getty Images) The research revealed that the literal ups and downs of individual human height closely track variations in two factors: diet and disease. Particularly, where these two factors are at work during childhood. If children do not get enough food to eat or cannot absorb nutrients because of diarrhoeal illness, say, their chances of sprouting into their full potential adult height are greatly diminished. "Bottom line," says William Leonard, a professor of anthropology at Northwestern University in Illinois, "the major drivers behind increased adult stature are improved nutrition, health, and in general a better quality of life." History is replete with examples of this height-health link. In the Western European late medieval period, after the Black Death had wiped out as much as 60% of the population, the survivors found they had access to plentiful food and uncrowded living conditions – both of which kept disease spread in check. People could thus grow relatively tall, with Englishmen just 4cm on average shorter than their fellow countrymen today. But in 17th Century Europe, heights hit a low point. The average Frenchman then stood no taller than 162cm. Severely cold winters, due to the Little Ice Age, slashed crop yields. Conflict broke out all over, from the English Civil War to the wars of Louis XIV of France and the 30 Years’ War in what became Germany. "Europe just kind of tore itself apart in the 17th Century," says Komlos. The 18th Century Industrial Revolution, which saw people packed into disease- ridden slums in cities, similarly stunted the populace. By the latter part of the 19th Century, though, the social upheaval had borne the fruit of improved agricultural production, running water and urban sanitation, as well as expanding economic prosperity. Western Europeans shot up the growth charts, and kept doing so for decades. This height-health link is still starkly visible today. For a modern day example, look no further than North and South Korea. The North ranks 188 out of 195 countries on the United Nations' Human Development Index (HDI), a metric of life expectancy, income and education. North Korean adult male height lags 3cm to 8cm behind the equivalent figures for their South Korean counterparts, whose country holds the HDI's 15th spot as of 2014. (