From a physiological point of view, it is hormones that control our growth. The researchers believe that the cause of the connection between environmental factors and growth lies in the hypothalamus, a part of the diencephalon. The hypothalamus releases so-called releasing hormones to the pituitary gland via blood vessels, which in turn control the release of other messenger substances, such as stress or sex hormones. These prepare us for increased stress or ensure the maturation of egg cells. Growth hormones such as somatropin and the insulin-like growth factor 1 (IGF-1) also belong to this group and are secreted in response to emotional situations. They affect the growth of the epiphyseal cartilages, which are located in the long tubular bones of the arms and legs. Once this space closes, we have reached our final body height. This happens at the age of 16 to 18 in girls and 21 to 22 in boys. Research suggests that stress, such as that experienced by severely neglected children, influences the release of growth hormones. Even in childhood, height comparison curves, known as percentile charts, are used by doctors to determine whether we are of “normal” height or whether we may have a medical condition. If a child’s growth is in the third percentile, for example, only three percent of all children are shorter – and pediatricians should then investigate possible causes. The World Health Organization (WHO) growth charts are based on the heights of children from all over the world. According to this classification, about 150 million preschool children worldwide are too short – and are automatically considered malnourished. “It is undisputed that there is hunger in the world and that malnutrition causes children to grow less,” Scheffler says. “However, we criticize the WHO classification, which, for the sake of simplicity, equates short stature with malnutrition. This pathologizes many people.”
Malnutrition and short stature
Research also repeatedly describes nutrition as a crucial factor for growth. In addition, there are regular claims that “short people have reduced physical, neurological, and later economic performance.” Taller children are supposedly equipped with better cognitive abilities and also earn more money as adults. In their book, the researchers polemically ask whether Italian men, who are 177 centimeters tall on average, are therefore less intelligent than Dutch men, who are on average 184 centimeters tall, even though there is enough food in both countries.
Are 150 million preschool children worldwide actually malnourished? To investigate this, Scheffler and Hermanussen traveled to West Timor, Indonesia. There, 50% of the children are smaller than the WHO reference. The people of West Timor are considered “stunted,” meaning, from a medical perspective, they have growth disorders. “However, we were unable to find any correlation between height and malnutrition within the population,” Scheffler reports. Instead, the children who are considered too small according to international reference standards were the fittest athletically and did not perform worse at school. From the researchers’ point of view, this clearly speaks against malnutrition as the cause of shorter stature. Rather, the lack of social mobility is responsible for this.
We are getting taller and taller ...
According to Scheffler and Hermanussen, social mobility is an important factor in determining how tall people become. To support this thesis, the researchers also drew on historical data and looked at the body heights of German soldiers from the 19th to the end of the 20th century. “From the mid-19th century to 1914, little changed and people remained relatively short. In the 1920s, people then became extremely tall. This was because there were more opportunities to climb the social ladder in the Weimar Republic,” the researcher says. In the 1930s, the children who had experienced the famine years of 1916 to 1919 as infants and toddlers grew up. “These cohorts were shorter than the previous and subsequent ones, but still several centimeters taller than cohorts who had reached adulthood before World War I. After another period of stagnation due to hunger at the end of the Second World War, we see a secular trend in both West and East Germany, i.e., a steady increase in height, which can be attributed to democratization on the one hand and social mobility on the other.” The thesis: the more opportunities for advancement a society offers, the more likely the lower classes are to orient themselves toward the height of the upper classes. “When hierarchical structures dissolve, for example through democratization processes, young people realize that they have opportunities for social mobility. They grow and thus also boost the growth of young people with better access to resources.” This makes the population as a whole taller.
At least as astonishing is the observation that East German recruits caught up by two centimeters within the first years after reunification, thus adapting to West German soldiers. “That’s enormous,” Scheffler says. This can be explained through the “community effect,” according to which the growth of children and young people adapts to their social environment: to their own family, but also to their peers in daycare and school. A study showed that the variability in height is greater before entering daycare than after: The differences in height between children within the same daycare group shrank within a year. “The shorter children tend to grow closer to the height of the taller children.” Scheffler also sees this confirmed in a study on the height of children with a Vietnamese migration background in Germany. The daughters of first-generation Vietnamese migrants were four centimeters taller than their mothers, while the sons towered over their fathers by eight centimeters. The human biologist refers to this as “strategic growth adaptation,” which she says is driven by the desire to “belong”. “We know from sociology that, statistically speaking, taller people are associated with higher positions and more money, competence, and dominance. This is accepted and also indirectly enforced.” This correlation has long been known from the animal kingdom. “It has deep evolutionary roots, but with our cultural abilities, we are of course more flexible. Not every tall person is automatically successful, and of course, shorter people can achieve just as much.” So it is not a biological law, but rather a statistical peculiarity.
Unlimited growth?
The Netherlands is currently home to the tallest people in the world. In addition to a functioning healthcare system and a balanced diet, researchers suspect that minor social differences are also responsible for this trend: in the mid-19th century, the Dutch were 163 centimeters tall on average, but within seven generations, the average height has increased by more than 20 centimeters. According to Scheffler, this development cannot be explained purely through genetics but is also linked to the civil rights introduced in 1848 under the parliamentary monarchy. Voices such as those of Scheffler and Hermanussen are increasingly being heard, who do not consider genetics, nutrition, and medical care alone to be the reasons for the increase in height in industrialized nations. However, too little is still known about the influences of environmental factors on our hormone balance to conclusively explain the secular trend.
The Netherlands has not recorded any further increase in height recently. “The increase in height over the past decades should be understood as an adaptation mechanism within a genetically predetermined framework that will eventually be exhausted biomechanically,” Prof. Scheffler says. “Above a certain height, for example, heart problems become more likely. From a biological point of view, it makes no sense to keep getting taller.”
Christiane Scheffler studied biology and chemistry. She has been working as a human biologist at the University of Potsdam since 1994.
READING TIP Michael Hermanussen & Christiane Scheffler: “Größenwahn. Zur Evolution biologischer Signale im sozialen Miteinander: ein Tuch aus 36 Fäden“ (“Megalomania. On the Evolution of Biological Signals in Social Interaction: A Cloth Woven of 36 Threads”)
https://link.springer.com/book/10.1007/978-3-662-69580-7
This text was published in the university magazine Portal - Zwei 2025 „Demokratie“. (in German)
Here You can find all articles in English at a glance: https://www.uni-potsdam.de/en/explore-the-up/up-to-date/university-magazine/portal-two-2025-democracy