Among the shortest people on the planet are the Maya people of Guatemala. Men typically float a few inches over five feet, while women do so somewhat below. However, the Maya become taller if they relocate to the US as young children. According to study by biological anthropologist Barry Bogin, Maya children born to Guatemalan immigrants in the United States are approximately four inches taller than their counterparts in Guatemala. This excess growth is carried over to the following generation. Even as children get older and the difference closes, Maya individuals living in the United States continue to be taller than their original people.
For a considerable time, researchers have noted a rise in height among immigrant populations globally. The standard causes for such growth point to improved sanitation and nutrition.
However, Bogin, from Loughborough University in England, and other scientists believe it goes beyond simply improved health. Compared to children raised in the United States, even children from wealthy families in Guatemala typically grow up shorter. A child’s growth trajectory is shifted to match that of children in their new community when they are moved from one civilization to another, according to Bogin, even if their lifestyle doesn’t alter all that much.
Evidence that genetics and nutrition cannot account for all human height variance supports his theory that height has a social component (SN: 5/13/20). Additionally, it is grounded in behavioral ecology research that demonstrates how many social animals’ growth adjusts in response to other members of their community—a phenomenon known as “strategic growth”—with dominant members frequently growing larger while subordinate members remain smaller in species with strict hierarchies.
According to Bogin’s 2021 proposal in Human Biology and Public Health, strategic expansion also propels human growth. According to his studies, a person’s height can reveal both the underlying political and economic circumstances of their culture as well as their perceived social standing within it. For example, in countries that are more equitable, the differences in height are smaller. Studies from Western countries indicate that people tend to grow taller when they relocate from highly stratified countries to more egalitarian settings. Bogin believes hormones—including those released when the body is under stress—may influence the social elements of height based on study on animals.
Everything sounds like it may manifest. When you observe other tall people, you get inspired to get taller yourself.
Sociologist Gert Stulp
Numerous scientists concur that living in a harsh environment can cause stress, which can stunt growth. Yet, they object to the notion that a person’s peers might affect their height. Sociologist Gert Stulp of the University of Groningen in the Netherlands adds, “It all sounds like… manifesting.” “You grow taller because you see other tall people and you want to be taller too.”
However, Bogin is a well-known expert on height. One of the most read textbooks in the subject is his third edition of Patterns of Human Growth. Colleagues are more likely to consider ideas that might otherwise seem absurd because of that reputation.
According to behavioral ecologist Peter Buston of Boston University, who studies strategic growth in clown fish, it is conceivable that social status affects human growth. Though he advises prudence. According to Buston, Bogin and his associates “haven’t yet done the studies that I would like to see done to make the strong case.”
The public health ramifications of framing height as at least somewhat socially influenced could be significant. Stunting, which affects 149 million children under the age of five globally, is extremely short in youngsters and may indicate socioeconomic deprivation as opposed to starvation, according to Bogin and others. Programs that reduce societal injustices may be more necessary in these situations than nutrition supplements, which are the standard method.
Clown fish, size, and social standing
In colonies of two to six fish, the clown fish that Buston investigates reside. The breeding female member is the largest, followed by the breeding male member. According to Buston, the remaining fish, none of which breed, get smaller and smaller until they are all roughly 80% the size of the fish in front of them in rank.
It was more than 20 years ago that Buston postulated that this strict structure serves to prevent conflict. It was recently discovered by a graduate student working in his lab that when a larger fish is brought into a colony to take the place of a smaller one, the larger fish is rejected. A smaller fish serves as a substitute.
Expulsion from the outdoors and subsequent exposure to predators would probably result in death. “There’s been really strong natural selection for individuals who can regulate their growth and turn their growth on and off,” according to Buston, at least in clown fish.
Social mammals also exhibit strategic growth. Think about meerkats, who reproduce 90 percent of the time in groups of three to fifty individuals, with a dominant breeding pair. Additionally, those two meerkats are usually the biggest. Smaller, frequently younger subordinates assist in feeding and caring for the pups; in the event that the dominant breeding couple perish, the largest nondominant animals take over.
In a 2016 study, meerkats in a wild group that were little and not breeding were given hard-boiled eggs as a dietary supplement by researchers, which caused the animals to grow larger. Even after egg supplementation ceased, dominant meerkats continued to gain weight in the two to four months following their ascent to the top rank.
The researchers speculate that this ongoing expansion may be explained by hormonal changes linked to a climb in the social order. Progesterone and estradiol are sex hormones that dominant females have in greater amounts than subordinate females. Furthermore, cortisol, the main stress hormone, is present in higher amounts in dominant males and females. In mammals, growth is regulated by sex hormones and cortisol (although elevated cortisol levels likely inhibit human growth).
Trade-offs may arise from growing larger, according to meerkat experts. Spending more energy on growth could reduce an organism’s capacity to resist sickness or shorten its lifespan.
Species that have extremely different mating structures from meerkats and clown fish may also experience strategic expansion. For example, male puku antelopes in Africa compete with one another for territory in an attempt to attract females. More scent-marking hormones are secreted by a male with a territory than by a male without one. The size of the territorial male increases in tandem with an increase in hormones.
Height is a conundrum.
However, it is still unclear what elements and to what extent human height is influenced. Undoubtedly, genetics plays a role, but not all patterns seem to be explained by genetics. Likewise with regard to diet and hygiene. Historical and contemporary evidence suggest that additional factors must be included.
For example, a comparison of 168,000 offspring in sub-Saharan Africa and India revealed that, on average, the eldest males in Africa were shorter than the firstborn sons in India. However, compared to African children of the same age and birth status, other Indian siblings were shorter. According to research published in 2017, Indian children are genetically predisposed to grow to the same height as children from sub-Saharan Africa, but only their eldest sons seem to be able to fulfill this potential. Unexpectedly, if diet or sanitation were the main problems, the wealthiest families in India displayed the greatest height differences between older and younger siblings.
Samantha Cox, an archaeologist at the University of Pennsylvania, discovered a comparable height difference in adult females in early Neolithic European groups. Despite having similar genetic makeup and access to resources, Cox found that females in North Central Europe (modern-day northern Germany) measured a few inches shorter than females in South Central Europe (southern Germany, Austria, and Slovakia) after analyzing ancient DNA samples from skeletal remains that date back approximately 7,000 years. Conversely, Cox’s team revealed in the February issue of Nature Human Behavior that males in both regions were of the same height.
However, compared to southerners, northerners showed a lot more outward symptoms of stress. According to Cox, this might be because northern Neolithic cultures had difficulty cultivating food. The fact that northern males recovered from that stress while northern females did not could be explained by some social aspect. Discrimination against women may have existed in the north. She remarks, “It appears fairly obvious that there is a preference for men here.”
These and other status-related variations in stature have also been noted in contemporary communities. According to Stulp, “it is undeniably true that people with higher social status are taller than those with lower status.” For example, there is a so-called height premium since taller people often make more money than shorter people.
However, the premium differs depending on the location, according to a 2023 study published in Economics & Human Biology. The height premium is generally lower in wealthier, Western nations like the United States and Australia than it is in Asian and Latin American nations. The researchers explain this disparity by pointing to the influence of environmental factors, which are increasingly erratic as poverty levels rise. Therefore, there may be a larger height premium in lower-income nations because individuals there are more inclined than those in higher-income countries to link taller stature with improved fitness and health.
rivalry between siblings
In a research comparing children in sub-Saharan Africa and India, the impact of birth order on height was greater in India than in Africa. In India, the average z-score of firstborns increased because the oldest son was taller than the younger siblings. The z-score for each cohort shows how many standard deviations there are from the reference population’s average height. The cohort is shorter the lower the score.
Child height in Africa and India according to birth order
For many years, economists have been aware that differences in height, particularly those pertaining to gender or class, might provide information about the social structure of a community. According to Joan Costa-Font, a health economist at the London School of Economics and Political Science, “we know that height is very sensitive to inequality.”
Overall population decline has been associated with inequality. These differences typically appear early in childhood and continue into maturity. Researchers measured the heights of over 37,000 kids between the ages of 4 and 6 from five wealthy nations in one analysis. Based on a standardized scale, inequality varies; the most unequal country was the US, followed by the UK, Australia, the Netherlands, and Sweden. Researchers found that children from the Netherlands and Sweden were taller than children from the other three nations in every socioeconomic band. Their findings were published in BMJ Paediatrics Open in 2019. And the youngsters in the lowest income band had the greatest variation across national boundaries.
According to the researchers, stressors like low social belonging and longer work hours for caregivers—which are known to impact health and potentially height—may be made worse by inequality, even in wealthy nations where malnutrition is not a problem. Generally speaking, nations with higher levels of equality provide robust social services that lessen these costs.
Growing socioeconomic parity may be the cause of the 140-year trend in height growth in Western Europe, according to Björn Quanjer, a historical demographer at Radboud University in Nijmegen, the Netherlands. That isn’t enough, though, to account for why certain populations are taller than others. The Netherlands has an average male height of 6 feet, 9 inches, compared to 5 feet, 9 inches to 5 feet, 11 inches in other parts of Europe.
According to Quanjer, “all Western European countries grew taller, but the Netherlands outgrew them.” It is suggested that high levels of education, a low rate of illness, healthy eating habits, and heredity could be the cause of the increased height. However, “the simple answer is we don’t know,” according to Quanjer.
Do people grow strategically?
Bogin and colleagues, such as pediatric endocrinologist Michael Hermanussen, speculate that at least some of this may be explained by strategic growth, as observed in meerkats and clown fish.
For decades Hermanussen has used European military records to uncover trends in human height variations. According to his analysis of conscript data pertaining to East and West Germans, East German conscripts were around one inch shorter than West German conscripts prior to the start of the reunification process in 1989.
Hermanussen, a private practitioner in Altenhof, Germany, found the height disparity inexplicable. Genetically, boys in East and West Germany were comparable. Furthermore, until the boys were around 12 years old, the heights of the two groups of boys were similar, indicating that nutrition was probably not a big contributing factor either.
The average height of East German conscripts rose steadily after reunification. They reached the height of West German conscripts in just five years. Hermanussen surmised that the collective development spike could be explained by the significant social and political upheaval that followed the overthrow of the notoriously manipulative regime in East Germany (SN: 5/16/23).
Some, according to Hermanussen, were dubious. “People believed that it had to do with genes, health, or nutrition.”
Hermanussen continued his study on a different population with statistician Christian Aßmann of the University of Bamberg in Germany and human biologist Christiane Scheffler of the University of Potsdam in Germany. In Swiss conscript data covering three historical periods (1884–1891, 1908–1910, and 2004–2009), they discovered what Hermanussen and Scheffler currently believe to be an indication of strategic progress. The study discovered that conscripts’ height tended to cluster in more connected localities when considering Switzerland as a single network with 169 cities connected by 345 routes. If a village was relatively small, then its neighbor was also relatively small.
According to Hermanussen, “the community effect was quite clear.” “Almost all of the individuals living in groups have similar heights.”
Furthermore, he discovered that while variations in height within a particular community remained constant, gains in height throughout Switzerland over time differed from district to district. In other words, everyone increased in height by about the same amount.
Before learning of the meerkat experiment, Hermanussen remembers thinking, “There must be something in the air.” What if, Hermanussen mused, the democratization of Europe—which had begun in the middle of the 1800s in areas like Switzerland and the Netherlands—was similar to rival meerkats becoming equal in size? Similar to meerkats, this equalization might result in a race between people based on height. Hermanussen surmises that in the absence of a strict hierarchy, people could constantly compete for social status. “People get taller because of this.”
Social scientists call this ability to move up the social hierarchy in human civilizations “social mobility.” Bogin believes that people in Guatemala are kept short due to a lack of mobility. There is a great deal of inequality in the country; according to certain surveys, a small group of people control approximately half of its wealth. The majority of Maya families are impoverished and have little opportunities for growth. Wealthy Maya and non-Maya families alike always face the danger of kidnappings for ransom and other violent crimes.
According to Bogin, people in Guatemala don’t have hope for a better future. “Growth hormones are blocked by stress hormones.”
Better food and a cleaner environment in the US definitely aid in the development of immigrants, according to Bogin. However, social variables such as living in a safer society and having hope for the future may also play a role.
The connection between status and stunting
If there is a social component to height, then the current public health understanding that links stunting solely to malnutrition may need to be reconsidered. Growth is definitely inhibited by starvation, according to Scheffler. However, being short does not always indicate starvation.
For example, Scheffler and colleagues recruited more than 1,700 children, ages 6 to 13, from three areas of Indonesia in a study published in 2020 in the European Journal of Clinical Nutrition: West Timor, one of the poorest regions in the nation; North Sumatra, a more affluent province with low industry; and Bali, a wealthy tourist enclave.
The children’s height and skinfold thickness, or subcutaneous fat, at different body locations were measured by the researchers. None of the youngsters who would have been considered “stunted” exhibited any evidence of malnutrition based on the skinfold thickness. Once again, the researchers discovered no connection between stunting and malnutrition after focusing on over 700 children in West Timor, where stunting rates varied from approximately 9 percent among children from the wealthiest families to 47 percent among the poorest.
Scheffler contends that stunting is a proxy for social poverty rather than hunger. “Students may or may not be malnourished, but malnourished individuals are not inherently stunted.”
“We are aware that inequality affects height very sensitively.”
Economist for health Joan Costa-Font
That could help explain a growing body of evidence, according to anthropologist Emily Yates-Doerr of Oregon State University in Corvallis, that suggests nutrition interventions have little effect on improving child growth. “It is challenging for global health professionals to feed people who are taller.”
Accurate figures about the amount of money allocated globally to reduce stunting are difficult to come by. According to a 2016 estimate, governments spend nearly $4 billion annually on addressing hunger-related diseases like anemia and stunting. Furthermore, a significant amount of researchers and policymakers feel that more funding is required. Height is a signal, and it must be acknowledged and comprehended. Because we get the wrong impression if we misread the signal, claims Hermanussen.
However, not everyone is persuaded that social standing has any bearing at all, much less a significant one, on human height. According to research, humans can demonstrate their dominance through behaviors other than height, such as wielding weapons or strolling in a group to demonstrate their strength in numbers, according to Christopher von Rueden, an evolutionary anthropologist from the University of Richmond in Virginia. He finds it “odd” that social standing is determined by height rather than, say, group combat prowess or muscular mass.
Furthermore, human cultures are intricate. Social networks in particular are dynamic, with users coming and going. It’s possible for other elements to overpower any signal from strategic growth.
The debate revolves upon one’s interpretation of human nature. In human civilizations, would a pecking order continue if other forms of inequality were eliminated? Or would there likewise be no need for a rating system? Social animals nevertheless create hierarchies even in the absence of complex political and cultural structures that are assumed to be the cause of human inequality, according to Bogin. What makes a community of equals among humans any different?
Bogin states, “We would still have a lot of variation in height if everything were completely equal for everybody.”
However, a large number of height researchers disagree. Cox adds, “Height seems like such a basic quality. If resources were evenly split, then height variations that Bogin and others attach to social standing would disappear too. I believe that many people would be shocked to learn how little we actually know about it.
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