“There is no obvious answer; it is not just about race or genes, but also because socioeconomic levels have greatly improved. And, of course, it’s not only happening in the Netherlands. It is a universal process that we are trying to understand better through this project,” explains Kok, Professor of Economic, Social and Demographic History at Radboud University (the Netherlands).

The study involves reconstructing the life histories of more than 80,000 people born between the years 1812 and 1922 by consulting civil registries of births, marriages and deaths. Back in 1850, the Dutch instituted a system of population registration, which they copied from their Belgian neighbors. This database is one of the cornerstones of the project, although, as Kok stresses, “the big difference (versus similar studies) is that we have records of the entire life course. We know the conditions people experienced in their early life stages: what situation this child grew up in, whether he or she was raised by a single mother or single father, whether there was a step-mother… But we can also delve further, and learn if they worked or not, were married r unmarried, who they married, whether tall children were likelier to get married, whether they had more children, and if those children were also taller… What is unique to our approach,” the researcher sums up, “is that we had access to full life-course data.”

The five-year project is now in its second year. Having completed the work of processing data records, they are now starting to look at the various factors potentially influencing the growth process: biological, genetic transmission, possible environmental effects, differences between town and country, changes in food prices, the disappearance of certain diseases… with special attention to the family environment.

Are the younger children within a family likelier to go hungry? Do smaller sized families enjoy better health? These are just a few of the questions that come up, and some of the tentative answers, which still need confirming, are particularly striking: “One preliminary conclusion is that a young boy who grows up with sisters will do better than one growing up only with brothers,” says Professor Kok. “Girls need fewer calories, less food than boys, we knew that already, but the effect is visible. The question is whether there is anti-girl discrimination. If there is one boy or two, are they given more food? Perhaps even more than they need? More than the girls? Does this discrimination pattern occur in every social group or only in certain periods?”

A historiographic study

The examination of military records, another key aspect of the preliminary historiographic study, has unearthed some fascinating information, Kok relates: on comparing the measurements of nineteen-year-old men with others taken at age twenty-five, “we discovered considerable catch-up growth: after the 19th century, average growth in this interval was five centimeters, but men who were turned down (for military service) for being too short grew a full twelve centimeters taller.” What the team now hope to ascertain is whether this statistic can tell us more about changes in the terminal age for growth, or whether it is another explanatory factor for the leap in height among the citizens of the Low Countries.

“Another goal of the project,” Kok continues, “is to learn what happens in the last stage of life: whether children who attained a certain height had more or less success in the labor market, or in the marriage market, because women prefer to marry a taller man. There is still a lot to be done.”

Professor Kok believes that the conclusions of his research could provide a template to repeat the experience in other countries. To this end, he will try to quantify the extent to which each study variable affects height: “The Dutch have grown some 20 centimeters since the 19th century, which really is a lot. But we want to break down that statistic. What percentage is due to the reduction in disease? How much of the increase owes to better food production and distribution? How much is because families are smaller? This is what we want to find out, before we present our results in three years’ time.”