How tall are humans supposed to be

The textbook Height, Health, and History by Roderick Floud, Annabel Gregory, and Kenneth Wachter states, "it seems safe to say only that the upward trend in European heights reflects the economic development of European nations and the increasing living standards of their populations.

Now let's look at some numbers. As reported in the book Height, Health, and History , the change in average adult male height in the United States over the last three hundred years did not follow a simple trend. From around to , the average height of adult American men remained effectively at around cm. Over the next sixty years to , the average height actually dropped from cm down to cm. Then over the next forty years to , the average height climbed back up, reaching the value of cm.

The average height of adult American men today is still cm. We can take a few things away from these numbers. First, there has not been a smooth trend in average height change over the last years in the United States. For most of this period, the average height has either stagnated or dropped.

Only during the brief forty years leading up to the Great Depression did the average height see rapid increase. Therefore, in the United States, an increase in average height is neither steady nor inevitable. Secondly, Americans today are not really that much taller than Americans during the 's. Three centimeters is less than the diameter of a golf ball. Therefore, a house from the 's that has its ceiling three feet too low according to today's standards is not that way because people were three feet shorter back then.

Such a house must have been built that way for another reason perhaps the inhabitants were too poor to afford the extra material for high ceilings. Both child mortality and healthcare expenditure impact life expectancy: we would therefore expect them to be strong determinants of the relationship between standard of living and average height. Total fertility rate the number of children per woman also interacts with these determinants, making it the second strongest socioeconomic correlate of height.

The role of fertility in high-income countries is marginal since fertility rates are already very low. But it gains statistical significance at lower incomes, where fertility rates are relatively high. In families where there are a large number of children, expenditure and food availability for each child is often lower. We might therefore expect that in countries where the fertility rate is high, health expenditure and nutritional quality per child is low, while incidence of disease is high.

In a pioneering study of Japanese immigrants to Hawaii published in , Harry Shapiro found there to be a significant difference between the heights of Hawaiian-born Japanese and the Japanese immigrant population. The underlying idea here is that migration from poor countries to rich ones may lead to dramatic changes between generations.

In a similar study, Marcus Goldstein found there to be differences in the heights and other characteristics of the children of Mexican immigrants and their parents, as well as with native born Mexican children. Height is partly determined by the interaction of different genes. Recent breakthroughs in sequencing the human genome have enabled researchers to identify variants of genes that are associated with height.

These variants have a large number of combinations; these can lead to a wide range of potential heights. Specific combinations of these variants are much more common to some populations than others. This could help to explain disparities in average heights around the world. Certain haplogroups — groups of variant clusters that are inherited from one common ancestor — have observable associations with height. For example, one haplogroup J1-M is most commonly observed in populations that spread from the Zagros mountains in Iran to the Arabian peninsula, particularly Yemen.

By contrast, one haplogroup I-M is most concentrated in Germanic-speaking Europe, and the Western Balkans, particularly Herzegovina. These regions are characterised by tallness, which strongly suggests a correlation between this haplogroup and height. Is height determined by genetics or environment? The short answer is that it depends on the countries you are comparing.

Differences in average heights could be due to different genes, different environments, or — more likely — some combination of both. For instance, the average male height in Bosnia and Herzegovina is cm — far higher than the global mean of cm, and even the regional mean of cm.

This height cannot be explained by high standards of living nor high animal protein consumption: its HDI is one of the lowest in Europe, and the ratio of animal protein to plant protein consumption is only 0. The cause in this case must be genetic: nature over nurture. Differences in average heights between North and South Korea tell a very different story, as told by Pak The two halves of the Korean Peninsula share a genetic lineage, but since the partition in there has been a great divergence in average heights.

While the average height of South Korean men increased by 3. This disparity is much more likely to be due to differences in standards of living: nurture over nature. The equation that determines human height is made up of many components. No single factor can predict height at an individual or even a national level. But overall, average heights can offer a unique insight into the genetic makeup and standard of living of a population.

We have looked in detail at how mean heights vary across the world. But this tells us very little about the distribution of heights globally, regionally or within in a given country. How do heights vary: do most people have heights very similar to the average; or do they span a wide range? Adult heights within a population are approximately normally distributed due to genetic and environmental variance. Height is partly determined by the interaction of genes with variants.

One of the basic rules of probability known as the Central Limit Theorem says the distribution of a trait that is determined by independent random variables, like height and genes, roughly follows a bell curve. This means the range of human heights in a population fall centrally around the mean height. The normal distribution of heights allows us to make inferences about the range.

If we know the mean and standard deviation of heights, we have a good understanding of how heights vary across a population.

Drawing upon height data from almost , twinned pairs born between and , one study investigated the variance in heights across populations through time, and tried to explain how much could be explained by genetics versus environmental differences. We see this distribution of heights in the chart. As an aggregate of the regions with available data — Europe, North America, Australia, and East Asia — they found the mean male height to be Women were smaller on average, with a mean height of Regionally, the standard deviation of male heights is largest in North America and Australia, at 7.

The pattern is the same for women, with 6. Some of the distribution of heights within a population is likely to reflect the degree of genetic variance. Differences in height within a population are not only influenced by genetic variance. Greater environmental variance within a population is also reflected by a wider distribution of heights.

The distribution of heights has therefore be used as one indicator of socioeconomic inequality in the past. In a population with perfectly equal access to nutrition and health resources, height distribution would only reflect genetic variation. Unequal access to these resources within a population means that wealthier individuals could have better health and nutrition, and therefore tend to grow taller than poorer ones; variance of heights therefore becomes larger.

In other words, resource-based variance due to income inequality is added to genetic variance, widening the distribution of heights. Some empirical evidence across a range of contexts would support this hypothesis. Members of the high castes — who had better access to nutrition and health resources — were 4. Furthermore, Ayuda identified a relationship between socioeconomic status and height among Spanish conscripts from to Height inequality, which is measured by the coefficient of variation CV , is therefore positively correlated with income inequality, which is measured by the Gini coefficient.

This relationship was observed in a study of Kenya during the 20th century, where the CV mirrored fluctuations in the Gini coefficient. It also compared the height distributions of Uganda and Togo, where average heights were roughly equal, but there was higher income inequality in the former than the latter.

Sure enough, the distribution of heights was wider in Uganda. So, both genetic and environmental factors have an impact on height variation. But which is the most important determinant? Heritability is measured between 0 and 1; the higher the heritability, the larger the contribution of genetics. Twin and adoption studies typically estimate heritability at about 0.

This means that the majority of the variation in height within a population is due to genetic variation, but environmental variation due to socioeconomic factors also has an impact. Accurately measuring the height of an individual is a straightforward task and so we should be confident that there is relatively little measurement error in the recorded data.

This is unlikely to be the case when measuring the height of skeletons. What is more, the techniques used to date skeletal remains such as radio carbon dating only provide a probabilistic estimate. Another factor to consider is the potential sample bias from the historical sources. Since the height data is largely composed of soldiers, criminals, salves and servants, these groups may not be representative of the wider population.

This problem has been highlighted by academics researching human height. In fact, the observed drop in height during the industrial revolution — usually attributed to the negative health impacts of industrialisation — can be explained by the labour market conditions that existed at the time.

By comparing the heights of soldiers in the US army with countries that enforced conscription we can see the bias more clearly. In countries that had conscription, the average height of conscripts was increasing over the period, meanwhile in the US where entry was voluntary, the heights of soldiers was falling.

All our charts on Human Height Annual change in average female height Annual change in average male height Average adult height by year of birth Average height of men by year of birth Average height of men by year of birth Average height of men by year of birth Average height of men by year of birth NCD-RisC to Average height of women by year of birth Change in mean female height over years Child mortality rate vs.

Mean male height Height of adult men Human Development Index vs. Mean male height Human heights over the long-run Increase in mean heights of females born in vs. Mean male height. The history of human height.

Male heights from skeletons in Europe, — Clark 2. Click to open interactive version. Regional variation in height changes. There are significant regional variations in change in average human heights.

Which countries have seen the greatest absolute gains in height? Some countries have seen much larger increases in average human height than others. Despite variation across countries, men and women globally saw similar gains: about 8 to 9 cm. Which countries have seen the greatest relative gains in height? Did heights across the world increase more for men or women?

Human height across the world. Here, we examine variations in mean male and female heights by country. How tall are men across the world? How tall are women across the world? On average, women are almost 12 centimetres shorter than men. Men from Timor-Leste, at centimeters 5 feet 3 inches , and Guatemalan women, at centimeters 4 feet 11 inches , are considered the shortest.

Authors used nearly 1, worldwide population-based data, such as publicly available measurement surveys, to estimate height for people from all over the world born between to What happened to the United States? Meanwhile, Americans aren't quite as tall compared with the rest of the world anymore. A century ago, American men ranked as the third tallest in the world, standing at centimeters 5 feet 7 inches. Now, they place as the 37th, with an average of centimeters 5 feet 10 inches.

Similarly, American women had ranked as the fourth tallest in the world at centimeters 5 feet 3 inches. Now, they stand as the 42nd tallest in the world with an average of While Americans didn't experience big gains in height, their body mass index "increased a great deal," the report found. Being tall has its perks. Being tall is associated with better health such as living longer, being less likely to suffer from heart and respiratory diseases, according to research.

Also, taller women are less likely to have complications during birth. On the flip side, authors noted that greater height is associated with certain types of cancers such as colon, breast and ovarian cancers.