Dutch men who grew up between sisters around 1850 grew taller on average than men who only had brothers. This is evident from research by historian Björn Quanjer of the Radboud University.

The average height of a population can say a lot about the development of prosperity and health in the country. Malnutrition, illness and heavy labor in childhood can significantly hinder growth. A person’s height is therefore a good indicator of the quality of life in their first twenty years, Quanjer’s research also confirms. But the historian found another striking factor related to body size: family composition.

To come to this conclusion, Quanjer analyzed data from Dutch men born between 1812 and 1922. To do this, he used data from the Historical Sample of the Netherlands. This organization collected the individual life histories of approximately 80,000 people from this period by using, among other things, birth, death and marriage certificates. To investigate the influence of family composition on height, Quanjer then compared this data with data from the Defense Department, which measured the height of all conscripts. For this reason, the research focuses specifically on men, Quanjer explains. “Simply because during that period only men were conscripted.”

Family size
Combining the data showed, among other things, that children from larger families were shorter than children with fewer brothers and sisters. “On the one hand, this has to do with nutrition,” says Quanjer. “In the 19th century, many families were one week away from poverty. An extra child meant less food for everyone.” But what also matters is whether a boy grew up mainly surrounded by sisters or mainly brothers. Boys with only sisters grew taller on average. “Perhaps they were better able to claim their share,” the historian said. “The composition of a household certainly matters.”

Genes versus environment
These kinds of differences are less significant nowadays, which has to do with the ratio in which height is determined by genetics and environmental factors, Quanjer explains. “Right now, about 80% of your height is determined by your genes, and only 20% by external factors. In the 19th century it was more ‘fifty-fifty’.” That difference became extra clear when the researcher compared the heights of father and sons. In the lower socio-economic groups the difference in height between them was a lot greater than in the higher socio-economic groups. “While they have a relatively similar genetic package.”

Maternal mortality
The study also shows that the death of a parent, especially the mother, had a negative effect on children’s height. Boys between the ages of 5 and 12 lagged behind their peers in growth when their mother died. This is probably because they lacked essential care, such as healthy nutrition and hygiene. In addition, it appears that infectious diseases play a major role. “The chance of coming into contact with infectious diseases was very high, certainly until the Second World War,” says Quanjer. “But how often and how seriously, that was also a matter of luck.” So how big you grow is a combination of your genetic potential, the nutrition to get there, and the amount and severity of diseases contracted that can stunt growth.

Stagnation in height growth
Nowadays that genetic potential is more expressed. Around 1850, the average height of Dutch men was still 1.68 meters. Nowadays that has increased to an average length of 1.84 meters. However, this growth has stagnated in recent decades. It is sometimes claimed that this is due to the influx of migrants who are shorter and therefore lower the average, but according to Quanjer this influence is greatly overestimated. “We see that children of migrants are actually closer to Dutch people in terms of height than their parents, because they also benefit from healthy living conditions.” According to him, the stagnation is therefore more likely to be because we are at the limits of our genetic potential.

However, that does not mean that we should no longer be alert to body size, says Quanjer. “We should always strive to be healthier and more prosperous.” Knowledge about body size as a prosperity indicator can therefore also be used in regions where this is normally less clear. Being taller also has disadvantages. Taller people appear to be more susceptible to nerve damage, which affects the nerves in the body. They also appear to be at a higher risk of skin and bone infections. “Becoming extremely tall is therefore not ideal.”

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